From the allocated to accounts button on either the permission set in the list or on the modify page you will be taken to a preset search for accounts that have that permission set. From here you have access to all the same actions as any other search including allocate and revoke permission sets.
Viewing the resource allocation
From the allocated to accounts button on either the permission set in the list or on the modify page you will be taken to a filtered view of the allocated tab in the resource catalogue. From there you can remove resources or select This view will let you easily remove resources from the permission set. You can also add others from the 'All' tab, but you will find it easier to use the Add button (see below).
Adding resources to a permission set
On the permission set details page there is an add button beside the list resources button.
This will bring up a list of all the resources that are not already allocated to this permission set - add them to the set by clicking on the add buttons on the relevant resources.
You can also allocate resources to a permission set directly from the catalogue.