Does anybody knows how to choose a mountain bike?

summerbreeze200

I am a female about 156 cm tall.   I am looking for a cheaper beginner mountain bike.  Are those ones for sale at Costco will fit me?  They are youth bike but since I am not tall, I am just wondering if I can just buy one that rides good from there.
( f+ A/ x; e. L, T  Rthanks