Hey Star welcome to the wonderful world of SW.
Is the stuff on the back white or pink/purple? If it is white you might want to remove it, it could be extra calcium which could make it a little difficult to control your calc level once you start getting everything together. I would prefer to add as needed not have a lot of it in the tank to start. If it is pink/purple it is probably coralline algae which would be a good thing.
As John said read read read read read and then read some more, the helpful articles are a great place to start and then the local library.
Golden rule number 2,856,259: Take it slow very slow, good things take time and bad things happen very quickly!
Be patient with it and let everything run its course (the cycle ect). Don't add to quickly or to much at once. It is a great hobby but it takes lots of patience and time. I know you don't want to look at an empty tank for a month or so but trust me it pays off in the long run!!!
Welcome again
Kevin