do the fish wisper back... ha
I'm 51 and and pounding on the compound movements. That is the key for gains. I still grow, at this age, it is very cool. Clean too by the way, as I will never have a need to get huge.
Since you are new to the weights game, keep poundage light , relatively speaking, in the 12 to 15 rep range. Let your ligaments and tendons get a feel for the new motions, the contracting and stretching, they are being put through. Your joints too will appreciate the slow introduction, before going heavy that is.
Pay attention to the squatrack in the gym, and introduce yourself to it. Do it on your very next visit. While there, practice the movement with an unloaded bar if you are capable. If not, do it without weight, all the while working on the the flexibilty needed to squat with the proper range of motion and the proper form. This is important. This could take weeks. Leave the ego at the door. Proper form is all that mattersfor now. The poundage will follow, and you will be repping 225 in a years time.
As far as your abs go, they are there, burried under the snacks you ingest while wispering to fish... but if abs are your game, look up front squat on youtube, as this will slay your core, like no other excercise.
Hope this helps get you going in a somewhat limited by useful direction.
Welcome to the board.