Yes @karensuestudios, you can log into your account using your Private Posting Key. I always use the postings key, you can also claim rewards from your wallet but if you attempt to make any transactions, you will be asked to provide your Active Private Key. This is a good way to increase security for your steemit account. I also don't store my keys on my computer.
There are some good posts about permission keys. I'll ass a link here once i find the one i had in mind.