How to sex ID my plant?

It's easier to tell by watching for formation of the little buds that will grow into flowers - these look like little balls on both sexes, and also on hermaphrodite plants, but the female buds will have little hair like extensions on them. Hermaphrodite plants are treated the same as male plants - unless you're wanting to collect seed, they are removed and disposed of, so you will need to check all the little balls you can find to see if some have no hair like extensions and other ones do.

Male plants tend to produce a thicker stalk with fewer leaves, so it is possible to tell before bud formation, but if you're only growing one plant, you have nothing to compare it with. Step by step guidance here https://www.wikihow.com/Identify-Female-and-Male-Marijuana-Plants