This has been asked a few times, in different ways.
If you are logged in as admin, and then you sign-up somebody else with their name and email, the sign-up will be assigned to your user account (since you were logged in when you signed up), so the signup will show up in YOUR list of events you signed up for on the main page, and you (as admin) will be the only one who can see them and clear those sign-ups. The confirmation email and reminder emails, however, will still go to the email that you entered when you signed up.
So, that particular way of doing things might be helpful if the volunteers don’t have user accounts on your site and you don’t want to create user accounts for them, or if you don’t want them to be able to view and clear their own sign-ups from the main volunteer page.
The second way you could do it is to LOGOUT of your admin account so that you are a guest user, and then when you sign up for something, my plugin will search for the email you use within the site user accounts, and, if it finds a match, will assign that signup to the user account with the matching email. Then, when that person logins to their account on the site, they will be able to view their sign-ups and clear any signups on their own (if you don’t disable the clear function for that sheet). With this method, you may need to first make the sign-up sheets publicly accessible while you are signing people up, and then you can log back in when you are done and change the setting back to hide sign-up sheets from the public (if desired).
Hope that makes sense!