all you have to do is: 1. open site manager on filezilla 2. add new site 3. give host address and port if port is not default port 4. communnication type: SFTP 5. session type key file 6. put username 7. choose key file directory but beware on windows file explorer looks for ppk file as default choose all files on dropdown then choose your pem file and you are good to go.
since you add new site and configured next time when you want to connect just choose your saved site and connect. That is it.