Izzyk,
On that screen you are trying to search for Properties. That is something slightly different. (Containers for domains not users) Here is the easiest way to give your users access to Target.
1. Log-in to the Experience Cloud.
2. Go to the Admin Console
3. Click into the Target product
4. Click into the Default Workspace
5. Add the user in here.
6. Adjust the "Role" column for the user in question depending on what access level access you want to give them: observer, editor, approver.
I just hosted an Office Hours session on this yesterday. If you haven't had a chance to view it you can check it out here: Adobe Target: Premium Workspaces
If you still have questions don't hesitate to reach back out to us in here or via call or email. Also let me know if this answer has helped you out.
Hope you have a wonderful rest of your day!