Can anyone tell me how to block emails on Gmail?

If you're talking about blocking emails. There is an down arrow button (underneath the print email button). In there you have the option of blocking the sender.
However, if that isn't enough, I usually set up a Filter that puts all emails from certain senders to folders that I have already created.

For instance, I'm a member of some groups on FB. So to declutter all the FB messages and notifications, I have a filter to put all FB emails into a FB folder.

For Spam mail, I have a spam folder that I put most spam mail in and usually go through and erase once a week.