To block spammers who are using your auction site, open the Admin Panel, click on the User icon (the 3rd icon from the bottom) and click Users.
If your site has many users, you may want to use the search function instead of manually searching for a user. To do that, enter the email address, username, or full name of the person who is causing problems on your site into the field that includes 1 in screenshot below, and click find.
To block the user, make the mouse pointer click on his/her entry and click Show more...
Two new options will appear. Click Block.
The user will now appear as Blocked in the listing and he/she will not be able to access your site any longer.