Hi Lori - I did a quick search on the forum & also couldn't find a tutorial (surprising - perhaps I should write one). Releasing an app on Play Store for the first time is a reasonably laborious task because you need to complete all the categores (Store Listing, Content Rating, Pricing & Distribution, etc...), however for subsequent updates it's pretty easy because all you have to do is upload the apk, put some "what's new" info in & update the description if necessary.
Here's a link to a tutorial on raywenderlich.com that should get you started. It's a couple of years old & the Console UI has changed a little since then, but the steps are still the same. If you've already signed the apk, you should skip down to the "The Google Play Developer Console" section. I'd recommend you give it a try & if you get stuck just post a question on the forum.
- Colin.