On your lubuntu machine run ifconfig -a to find the ipaddress assuming you don't recall the host name. Then open a terminal on your Ubuntu machine and type ssh user@ipaddress(or host name) and then type in the password for the user. Alternatively you can setup a private key for your Ubuntu machine and upload the public key to your lubuntu machine, eliminating the need for entering a password.
- Leave pass phrase blank or enter one. Entering one is more secure.
- ssh-copy-id user@ipaddress
- Enter password for user
- Enter pass phrase if created
From then on, you will only need to type ssh user@ipaddress to log on to your server. You can research ssh config file to make it even simpler if you prefer. Hope this helps.
If not... What error or problem are you actually having? Detail is everything.