Just remember the starting position: Bar over the middle of your feet and make shins touch bar. That's about it. You should find your shoulder blades are directly over the bar. That's the basics sorted.
The more difficult bit is at the top of the lift i.e. knowing when to stop extending. You shouldn't "lean back" as it were at all. (Which from the vid you've posted, it doesn't look like you are doing so no worried there!)
The more difficult bit is at the top of the lift i.e. knowing when to stop extending. You shouldn't "lean back" as it were at all. (Which from the vid you've posted, it doesn't look like you are doing so no worried there!)