There are two options when it comes to manually unsubscribing your users:
option 1: Unsubscribe users one by one in Microscope (see here).
option 2: Unsubscribe users via list upload.
Unsubscribing users via list upload
Data Management --> Smart Segments --> Upload
Name your list upload and description, and select the import option "Import a comma separated .csv/.txt file"
Your file should include the headers "email" and "date unsubscribed", see example here:
More info here on uploading lists.
Important things to note:
- make sure to have the correct date format.