How do i gain weight properly?

Well im at 16 years of age and 171 cm and currently around 126 to 130lbs and i wish to hopefully reach a high weight of 138lbs. My body is ripped but yet the muscle mass isn’t very thick as in saying to ufc fighters.

I heard of articles saying that only do workouts for 45 minutes because the testosterone secretion would only last for that specific period of time, but what would happens if i were to want to do some cardio and verticle leaping excercises after the weight lifting workout in the same day is it possible and if so at what specific time would be bestest?

I usually workout and do swimming. My schedule goes like day1 upperbody upper back , day 2 abdominal lower back then cardio for 1 to 1.5 hour which includes the verticle leaping exercises or someday i would go swimming for 1 hour swimming contant no stopping.