"I do not know how to use the computer."
Translation:Je ne sais pas comment utiliser l'ordinateur.
"Connaitre" is know in the sense "heard of" or being familiarized with the existence of something. You can "connaitre un logiciel" (know that a certain software exists) but it doesn't imply you know how to use it. It is much more frequent with people: "Je connais Jean." - "I know Jean" or "I've met Jean".