It’s usually a good idea to use different ssh keys for each server or service you use, but it can be a little tedious to specify the key to use each time you connect, so here is what to add to your ssh configuration file (usually at ~/.ssh/config) to have it automatically pick the one you want.

If you have a ssh key named id_myserver in your ssh directory add this to each server in your config file for which you want to use that specific key.

Host myserver
  IdentityFile ~/.ssh/id_myserver