With Portfolios, you will set up both an index page for your portfolio, and you will also set up individual portfolio pages. A featured image (i.e. thumbnail) for each of the portfolio pages will be shown on your portfolio index page.
For example, let's say you have a set of images of different fruit you want to put into a portfolio. You might set up an index page called "Fruits," and you will set up individual portfolio pages for each different image -- e.g. an image of an apple, an image of an orange, an image of a banana, etc. When you finish, your index page will have thumbnails from the different portfolio pages on it (an apple, an orange, and a banana, etc.). Clicking on those thumbnails will take the visitor to the the individual portfolio page with a larger image and other info if you like.
You can have multiple portfolios by creating different portfolio categories. You can then either choose to show just one category on an index page, or you can show multiple categories on an index page (with the ability to filter by the different categories).
Follow the instructions below for setting up portfolios.
Set Up Individual Portfolio Pages
It may be easiest to start by setting up your individual portfolio pages first.
As an example, lets say you want set up 3 individual portfolio pages -- one for an apple image and text, one for a banana image and text, and one for a orange image and text.
Let's start with the page for the apple image and text.
Go to Portfolio > Add New. You will see an editor screen very similar to a regular Post or Page.
You can place any text, images, or other media you like in the editor just as you would for a Post or a Page. This information will appear below your main image at the top of the page under a section called "Job Description."
In the spot for the Featured Image, place the image you would like to appear on the portfolio index page. Once published, this image will also appear at the top of this individual portfolio page as a full-sized image.
Place the Portfolio Page in a Category
Next, you'll want to place your individual portfolio page into a category. This works the exact same way as it works for posts, but in this case you'll have categories for your different portfolios.
If you don't already have categories for your portfolios, you can set them up either by going to Portfolio > Categories, or you can create a new category directly on the portfolio page, just as you can do with a regular post.
For example, let's say you want to create a portfolio category called "Fruits." Just add it to the categories on the right hand side of the portfolio page.
This will automatically put the page in that category.
Choose Skills if Desired
You will also notice on the right hand side a section called "Skills." This works somewhat like categories. You can choose to add what skills were involved in creating your project. These will appear in a special section of of the page once it is published.
At the bottom of the edit page, you will also see a section for options that let you do things such as turn on/off the sidebar, link your project, control heights and widths, etc.
And here's a look at a published individual portfolio page. Notice the sections under the main image at the top. These appear automatically if you enter the info for them as mentioned above. You'll also notice "Related Work" thumbnails. These are taken from other pages in the same category.
Set Up the Index Page
To set up your index page, add a new Page to your site and name it as you like (e.g. Fruits). This is a regular Page you are adding. It will become a Portfolio Index Page when you assign a portfolio template to it.
To assign a portfolio template to your page, go to the right hand side and use the Template Pulldown Menu. You will see options for different portfolio styles.
Choose the Categories to Display (+ Other Options)
Lastly, you'll want to navigate to the bottom of the index editor page and find the Portfolio Options section there.
Here you can choose which portfolio categories you would like to display on the index page. If you choose more than one, filter buttons on the published page will automatically appear, allowing the visitors to filter by categories.
To choose more than one category, hold down the Command (Apple) or Ctrl (Windows or Linux) key while selecting.
You can also choose other options in this sections, such as whether to display your sidebar on the page or not.
Here's a published index page displaying two different categories (Dogs and Fruits). Notice the buttons to filter the categories.