Holding the Guitar - Standing

Your guitar is probably most comfortable at about chest-level. You can angle the guitar so your left hand is higher than your right hand.

Because you're aren't yet comfortable fretting the neck with your left hand yet, you don't want your guitar strap too low. It's going to be easiest if you keep your guitar high - about chest-level. This makes playing easier for your left hand. Later, after your left hand is better conditioned, you can lower your guitar strap to a level that is comfortable for both hands.

Playing with the strap low looks cool, but it really complicates your left-hand technique. You probably can't point to any first-rate players - Van Halen, Malmsteen, Satriani, take your pick - who play with their guitar around their knees. That sort of thing is just for show.

Make your life easier. Keep your strap high, at least for now.