For the bans to take effect, go to Site Manager -> Settings -> Security & Membership -> Protection, select the appropriate site, check the Enable banned IPs check-box and click Save. The bans should take effect now.
 

 
Users attempting to perform an action from an IP address that is banned should get a page with the following message displayed in their browsers.
 

 

This is the default banned IPs redirect page, which can be found at ~/CMSMessages/BannedIP.aspx. You can create your own page and set its URL in Site Manager -> Settings -> Security & Membership -> Protection -> Redirect banned IPs to URL.