Hi djsage, welcome to the forums.
To connect the MC4000 to your soundlink you will need a RCA to 3.5 mm cable such as this one here from Amazon.
There are lots of good beginner DJ resources to be found on Youtube such as Club Ready DJ School - don’t let the fact that he uses Pioneer gear put you off, the theory that he teaches can apply to most DJ gear.
Good luck with your new gear when you get it.