The first decision to make with alpacas is whether to buy your own or infiltrate someone's private alpaca farm. The pros of buying your own alpaca are 1) convenient alpaca lovemaking in the privacy of your own home 2) know the alpaca isn't going to sleep around on you 3) can build a meaningful relationship that transcends anonymous and hurried outdoor lovemaking.
Cons are 1) can be messy if kept indoors 2) expensive to buy and hard to rent them for sex purposes 3) can get boring if you just make love to the same alpaca all the time.
If buying an alpaca is too big of a step for you, then you can go sneak in to an alpaca farm. Obviously, late at night is generally the better time to do this. Alpacas are very smart animals and they will know what you are there for. So if there is a male alpaca around he will probably want to fight you. You will have to prove your superiority but their fighting skills aren't too good so just dodge its attacks and then you want to counterpunch him in the face or neck. A few of those and he'll grudgingly back off and let you do your business. If you lose to the alpaca stud then he will probably trample on you a little bit and some particularly vicious breeds of alpaca have even been known to forcibly sodomize human trespassers which you may or may not enjoy a furry throbbing cock in your ass. If you lose then you may want to come back later.
After that is taken care of then you want to approach the female alpaca from the behind and proceed to insert your boy parts into her girl alpaca parts. I recommend only female alpacas because it would be very embarrassing if someone you know caught you having gay sex with a boy alpaca. Anyway, you do not have to worry about buying her dinner or warming her up or sextalking her or anything like that. This is very natural to these animals. They will just think you are a male alpaca so it's not like it's rape or anything.
Enjoy the delicate and tender caress of the alpaca vagina and feel free to cum inside the warm alpaca pussy because unless you are a boy alpaca it is very hard to get them pregnant. Afterward you can pull your pants up and run off into the woods or if you are particularly sensitive you can cuddle with your new alpaca girlfriend or maybe even feed her some carrots.