Congratulations! Glad your first brew day went well. You'll find many different schools of thought on how to "harvest" or re-use your yeast. Since you're just starting out, may I suggest, once you've packaged your beer (either bottle or keg), research washing yeast. Since your first attempt was a darker beer, you will want to leave behind as much of the trub as you can in order to get "clean" yeast.
Washing yeast is deceptively simple and easy. The only extra equipment you will need is a large (quart) mason jar, and space in your refrigerator. Here it is in a nutshell (it's worked for me):
Once you have racked your beer into your bottling bucket (or keg, if you go that route), clap the lid back on the fermenter. (leave the airlock in place). Fill your quart mason jar with water, plus about 1/2 jar more, pour it into a pot, and boil it for at least 15 minutes. Once the water is cooled down to at least 170, pour it back in the jar, close it tightly, and refrigerate to get it to room temperature. (Side note - you can also do this step before you rack your beer into your bottling bucket or keg, saves time.)
The next step can be messy, so do it in an area that's easy to clean. Once your water is chilled down to room temperature, pour it into your fermenter on the yeast cake. Close the fermenter, and shake it well. Let it sit for about 20 minutes, this will let the trub settle to the bottom and the yeast will float on the top with the boiled water. After 20 minutes, pour this off into your mason jar (handily sanitized with your 170 water), leaving as much of the trub (darker layer that will be grainy) behind. Seal the jar, and put it in the fridge. And there's the yeast for your next batch! You can pitch it as is (after pouring off the beer-colored liquid that will have risen to the top), or you can make a starter with it (do some research on this).
Easy peasy, and can save you lots of $$$$.