To view the members of a Crowd, go to the crowd Profile page ellipses > Crowd membership. This will allow you to filter the existing members of the Crowd by a number of different fields including Role, User Type, and Department. You can also search for individual names using the search bar.
These filters can also help with adding members to the Crowd. This can be done by simply toggling the 'Membership' field to 'Non-members', then use the other filters to find the users you want to add. Users can be added individually using the 2+" symbol on their profile card, or all can be added at the one time using the 'Add all' button at the bottom, which will add all of the non-members you have filtered for
The second way to add users to a Crowd is though the manage Users menu. Go to Admin > Users > Edit > Crowd Membership and Permissions > Edit. You can then select which Category or Crowd the user will be a member of. You can also set user permissions from here