So, im making parkour, and I was wondering how you set it to where: when you step on a block, it saves it as your spawn point? That way people dont have to do it all over again?

/checkpoint

do it I dare you

More complete answer:

There is a special MCGalaxy block that appears invisible, which is named "checkpoint"
You can use /checkpoint (which turns all blocks you place into checkpoint blocks) then place a block  on the area you want the checkpoint to be. You'll have to make sure you turn it off again with /checkpoint or /abort.
The reason /checkpoint works is that if you type the name of any block as a command, it automatically turns all blocks you place into that block. Useful for MCGalaxy blocks that aren't available from the menu.

My preferred method is to stand where I want the checkpoint, then do /place checkpoint. This way I don't have to toggle anything, since it's one-and-done.