Add SSH Public Key to Server Manually adapted from linuxhandbook.com

keys.sh

# get the key you want to use
cat ~/.ssh/id_rsa.pub

# it will show you your public key (here's mine)
ssh-rsa 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 ofjolivares@gmail.com

# Create ssh directory in the user’s home directory (as a sysadmin)
mkdir -p /home/user_name/.ssh && touch /home/user_name/.ssh/authorized_keys

# Now open this /home/user_name/.ssh/authorized_keys file with a text editor
# like nano and add the public key of the user here:
nano /home/user_name/.ssh/authorized_keys

# set file permissions
chmod 700 /home/user_name/.ssh && chmod 600 /home/user_name/.ssh/authorized_keys

# change the ownership to the user:
chown -R username:username /home/username/.ssh