On your host

cat ~/.ssh/id_rsa.pub # if you don't have one create run: ssh-key -t rsa
# copy the content of the file into **authorized_keys** on the target host

On the target host

cd ~/.ssh/
ssh-keygen -t rsa # press enter twice
cat id_rsa.pub > authorized_keys
echo 'YOUR_PUB_KEY' >> authorized_keys