Collections are now referred to as Filters in 7.x
Go to Manage, Filters.
I always create a folder for Filters that I create vs those that come with the product.
In your folder, Right Click and choose New, Filter.
By default, the filter definition should be set to Query Mode: None. This means you are not defining a query but rather specifying resources to add. Click the down arrow to the right of filter definition. You should now see Inclusions and exclusions as 6.x had.
Add PCs individually by clicking on the no resources found.
Add from a file by clicking on the document icon.
Add other filters by clicking Select a filter.
Exclusions work in the same manner.