How do I connect to FTP using Filezilla?

You should be able to use your Linode's root credentials over port 22 to access FileZilla. If you're having trouble connecting, we have a more comprehensive Linode Community Questions post that I've linked to below that goes through some troubleshooting advice.

I can't connect using FileZilla

You may also want to check your firewall settings, determine whether root or password login is disabled on your Linode, and consider resetting your root password.

Did you set up an ftp server on your Linode? ftp is not set up by default on a Linode because it is (inherently) insecure.

Is (s)ftp open through your firewall?

-- sw

Hello, everyone!
Thank you very much for all the replies.

It turns out that resetting the root password was the key to my problem. I can now log in through Filezilla.

Thanks again!