i thought the whole point of knowing your private key, like on a paper wallet is so you don't need wallet software.
No. You've misunderstood. It would be extremely difficult to create and sign a transaction by hand.
The purpose of having your private key on paper is that it can't be hacked or accessed by viruses, and you won't lose it if your hard drive crashes. It's fine for long term storage of bitcoins that you don't intend to spend any time soon.
so in order to transfer from a paper wallet you need software?
Yes.