Beginner couple D/s 101
So first up lets define what you're doing here, you are submissive and your boyfriend is the Dom so number one, your job is to please your Dom.
So what does that entail? Well it can really be anything as long as it's something he enjoys, if you enjoy it too that's a bonus but not required. Generally though a real sub will gain pleasure just from knowing she has pleased her Dom aside from any other enjoyment.
One of the trickiest things to get started with is moving into the sub mindset, assume nothing, never demand and do as you're told. Now if this is a bedroom D/s thing only (and it almost always is) things will be "normal" at other times so its a good idea to have a way of signalling you want to play. This can be as simple as you putting on certain clothing or assuming a position or pose that indicates to him "come get me". However as I mentioned before don't push it, if he doesn't take the hint accept that, leave it for now and try again later. Of course done right it can be pretty hard to resist, try getting dressed only in nice underwear kneeling with your hands on your head and see if he just walks past.
Next there is learning how to talk like a sub and again this can be difficult to start with, try saying "Would you like me to suck your cock Sir?", "Please Sir will you cum on my face?" or "I've been a bad girl Sir, will you please spank me?". Do they come out naturally or seem silly? If they seem silly you will need to work on that, he may not like the "Sir" part and if so don't use it but you get the idea.
Now putting all this together for a practical first lesson I noticed you listed outdoor/public/exhibitionist in your likes so try this.
Together take a drive to a fairly quiet location and pull over on a back road. You both get out and on the off road side of the car he stands leaning on the car, you kneel and remove your top (can be top fully off or just unbuttoned, or top and bra off, even fully naked this is his call). You then take out his cock and suck him off, when he is ready to cum ask him how he wants you to finish (swallow, cum on face, cum on tits, etc) and only when done and when he says can you put your top back on. As a mark of respect do not clean cum unless/until he tells you to and never ask to clean up, simply dress and carry on.