I am new at all of this.
How can I take the grittiness out of my buttercream?

Hi and Welcome to CC, furgerson5.

Decoding CC acronyms:

http://cakecentral.com/cake-decorating-ftopict-2926-.html

Are you making (American) powdered sugar b/c?

Sifting your powdered sugar before mixing will remove any clumps (which really can't be mixed out).

If you're frosting with a crusting b/c, it's important to cover the bowl (when not in use) with a wet cloth to prevent the outer layer of frosting from crusting. (If you mix the crusted outler layer back into the frosting, you will notice a gritty texture.)

Other than that, it would be necessary to know which recipe you are using (as there are other types of frosting).

Here's a thread you might find useful....

Everything you ever wanted to know about making your 1st tiered/stacked/layer cake:

http://www.cakecentral.com/cake-decorating-ftopict-605188-.html

HTH