How do I start strenght training?

I'm off school for two weeks so I'm planning on starting to strength train with weights like 5-20 lbs. How do I start, how of ten should I do it. My goal is to build upper body muscle and gain strength around my body because I've been noticing small slivers of fat around thin parts of my body like my triceps and back. Also how should I eat, my mom isn't okay with me watching my weight because I almost got an eating disorder before
How do I start strenght training?
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