Considering you care about her and this is an actual relationship:
Strangely, I find it easier to escalate to sex than to a bj haha.
Anyways...find a good place first that's private and preferrably there's a couch or bed near...or if the ground is comfortable enough
Then, start kissing..then touching..and once your clothes come off and you're still lying down...I would suggest two ways..
1. You turn over and get on your back..continue kissing for a little longer...then slowly sit up..and dont hold her down...but kinda touch her in a way that says "stay down there"...hard to explain but that's one wayI've done this before...usually works pretty well
2. 69 hah...you have to start though...once you're down on her..you want to start off normal...then kinda tilt your head and start moving your body around...don't just suddenly flip over..but ease into it..I'd be a little more hesitant towards this...simply cuz shes young and will prolly feel uncomfortable with 69. Idk why but i've tried to get three different girls to 69 before, and one said it was just weird, another said it just wouldnt work, and another just didnt want to. Idk why, but unless the girl is pretty kinky, I doubt she'll go for this.
I would instead recommend fingering her (which i hope you've done by now), and then hope that she returns the favor. This can usually work pretty well. Like you finger her, and then after doing that for a little bit, if she doesnt move her hand down to your d*ck, take her hand it move it down there. Give her a minute or so, and if she doesnt switch to her mouth, say this: "Hey blah blah?" "Yea?" "Im not really a huge fan of handjobs/I dont really like handjobs" At that point, shes prolly wondering why you took her hand and put it down there in the first place. Hopefully then, unless shes completely stupid, she will realize that you want head.
If it any point she says, "oh i dont like giving head" (dont be alarmed, MANY girls hate giving head), say this: "Well you gotta return the favor somehow..." Hopefully then she'll get the point that you want to fvck. If you feel uncomfortable saying that, (which you shouldnt be, i mean shes pretty much your gf you should be able to say what you want), then do as I said below. If still no success, then ditch this girl.This leaves her with two options...1. do nothing...2. 69
For sex,
1. if you guys skip the bj...just continue as normal...
i dont know exactly what you're having toruble with..but in general, once her clothes are off,a nd yours of course...i dont know where you're having trouble..when you're bout to 'enter' her...she'lltell you stop if she's not comfortable..or she'll move away or something..just dont do anything rushed cause it'll remove that option for her and you'll loook like you're in a hurry haha