Most saddles sit on the shoulder blade, you can feel a bone and when it goes down that's the end of the shoulder blade. Most saddles sit on there.
To get the saddle place correct you need to have your horses leg fully extended and mark it with something, and place your saddle behind that.
Then you'll need shims to make the saddle higher and more comfortable 1 or 2 shims are recommended.And also if you want your gait to improve do transitions. Trust me it works! Hope this helps, cowgirls
Oh and looking at a you-tube video would also help you. Just write in 'saddle position and shims'