Lube?

Okay so like me and my boyfriend have been going at it raw most of the time that we’ve had sex. We only used a condom once and it was because I was in my period. But other than that we haven’t. We thought I was pregnant once cause I missed my period and started feeling sick. I took a test but it was negative. We both decided that we need to be more careful and use protection. My friend hooked me up with some condoms cause I couldn’t get them. He also hooked me up with flavored lube. I don’t even know how to use that? Is that even safe? Is that recommend? Tell me you’re thoughts and advice on how to use it please !!!