Opk waiting or right away?

Janelle • I`m 30 I have a daughter that is 6 and considering another since being divorced and being a single mom I now I met a man that loves me and my daughter dearly so he has no kids so looks like maybe soon
So once I get a positive line on an opk should we have sex or waite 12 hours? I heard having sex as close as you can to ovulation you have better chances of conceiving a boy and thats what were hoping for since we have a girl already.