Well ... Plain and simple - I don't know what to do

I'm TTC baby number 1, and I'm not sure when I O. I know there is an OPK but I haven't tried that yet. I also heard about charting temps but I'm not too sure how that works.
I've always been preventing pregnancies, and now my and DH feel ready to support a little Jr
Can anyone help me get started
Thanks in advance!