linux : ssh using identity file

1. generate ssh key on your target destination
  log in on your target destination computer and generate ssh keys:
   # ssh-keygen -t rsa

2. authorize generated key on your target destination
   append generated key to authorized keys:
   # cat id_rsa.pub >> authorized_keys

3. test connection using identity file
  copy identity file id_rsa to the computer where you'll connect from, then try connecting using that file
   # ssh -i id_rsa <user>@<destination ip/domain name>