Run the following command, some questions will be displayed, in my case I just pressed enter until the end:

ssh-keygen -t rsa

Run the command below replacing "edsonjunior" with your username and it will display your SSH key:

cat /home/edsonjunior/.ssh/id_rsa.pub

In this example I use github, after generating the key and copying it, go to settings > SSH and GPG keys > New SSH key, generate a title and insert your key, after clicking on Add SSH key.

If you generated the key correctly it will be accepted and from now on you can use your ssh key however you want.