Any tips for a newbie in the gym?

My boyfriend don’t want me working out but yet cuts me down telling me I’m not skinny but am so I really wanna get in the gym for myself but no idea where to even begin. I weigh 120 and kind of wanna tone my body and gain some muscle and stuff but I don't know how to go about anything and of course he won’t help me.
Any tips for a newbie in the gym?
Post Opinion