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 will get a page with the following message displayed in their browsers (the HTTP response code of the page will be 403.6).
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.