Mac and Linux systems have builtin OpenSSH tools to connect to your server. It is fine to use the command ssh -i </path/key.pem> <user@IP> , but you can avoid typing it every time by adding the key to the authorisation agent:
ssh-add <key>
Now you can SSH in with
ssh <user@IP>
Optionally you can also create a ssh shortcut to avoid typing the username and IP. To do so, create the file ~/.ssh/config on your Mac (if it doesn't already exist) using this template:
Host <shortname>
HostName <your_ec2_ip_address_here>
IdentityFile <~/.ssh/youridentityfile.pem>
User ubuntu
Now you can SSH in with
ssh <shortname>
To check what keys are added
ssh-add -l
If you want, you can view your server’s public key which was created and stored when it was set up
less .ssh/authorized_keys
If you get errors about permissions when trying to SSH in, you may have to modify the key file’s permissions with chmod
chmod 600 <file>
Check a file’s permissions with the longform list command
ls -l
See output like -r——–@ 1 user staff 1696 11 Jun 19:14 /path/yourfile.pem
Basically the first ten characters before the “@” indicate permissions and you want to see only dashes or “r” after the fourth character. man chmod has more.
More info about permissions here