Now if you already have a snap press or even pliers, you can attempt to do this yourself. It's very easy to remove the velcro with a seam ripper, just go slow because you don't want to snag the PUL (the outer material) and create holes or runs. Then you need to mark where the snaps will go. The easiest and most fool-proof way to do this is if you have a diaper with snaps, you can create a pattern from that. Otherwise you have to measure and figure out where you want the snaps to go. The most popular configuration is shown above, with two rows of snaps across and two snaps on each wing. This is also the way bumGenius Elemental AIOs have their snaps applied. See below.
Some people prefer to put only one row of sockets across with two studs on each wing, arranged horizontally. This is a personal preference only.
As you've probably noticed from the pictures, you can have the snaps match the color of the diaper, or not. That is also totally up to you. KAMsnaps sells bumGenius color-matched snaps for a perfect match, if you choose. Or you can have fun with it and choose complimentary colors or even use two different colored snaps on one diaper. I'm a traditional type of gal, so all my diapers have matching snaps. :)
Here is a helpful video if you plan on doing this yourself.
Now if you don't have access to a snap press or pliers or just want the ease of having someone else do the work for you, I highly recommend Heather at http://www.convertmydiapers.com/. Both times I sent my diapers out to her, I had them back in 10 days. That includes shipping time both ways. Her website describes prices for most popular brands of diapers, you choose the configuration and color of your snaps, and then you pay shipping both ways. I did send my diapers in with the velcro already removed, so I'm not sure how much time that saved in the process as far as getting my diapers back quicker, so keep that in mind. She does offer a discount if you choose to take care of this step on your own.
There are other diaper conversion sites out there, but I haven't used them, so I can't tell you what their turnaround time is or quality of work.
I hope this post has given you a better idea of how to convert your diapers yourself or get them converted by someone else. Happy Diapering!