Total newbie

So I am totally new at this whole "planning" a baby thing and I'm kinda clueless on some of the questions this app is asking me to answer. For instance, I have no idea about my mucus or how in the world I'm supposed to check my cervix. Both of my 2 kids were surprises for me so now that I'm planning baby #3 I'm totally lost on what to look for. Any advice at all would be great because I'm feeling a little discouraged seeing as we have been trying for like a month and a half with no luck. Does the fact I just quit the depo shot in mid to late September mean anything? Please help!