This is bad advice for someone new to DSLRs. Please don't take offense. Ideally, focus screens should only be handled while getting replaced. It's very, very difficult to clean them in-place without making matters worse.
Focus screens should not be handled, period. You need a special tool to do the job and even then it can be dicey.
If it were my cam and it there was dust in the viewfinder, I'd remove the focus screen (using the special tool) and use a blower once it's outside the camera. If dust remains, I'd use a special focus screen cleaner from Visible Dust (
Visible Dust Focusing Screen Swab (12-Pack) 3530044 B&H Photo) along with their solution to get the stubborn dust off.