My suggestions are as follows: use a lubricant to make it more comfortable for you. I prefer water based lubricants. Some women find that water-based lubes containing glycerin or sugar can potentially cause yeast infections, particularly if they're already prone to getting them. This is often the case with some flavored lubes, which are for external-use only and are not to be used inside the vagina or anus. One minor drawback is that water-based lubes can dry more quickly than other forms of lubricant; however, adding a bit more lube, water, or saliva can reactivate its slippery properties.
It will likely be uncomfortable and maybe even painful for your first experience in the rear, but there are positions and products that help with that. One position to try is to lie as if you are spooning, he can enter easily from that angle, and lying on your side will allow you to relax a bit more while he is entering. Also, in my experience, it is easiest and less painful if I push back against him, instead of him pushing into me. The reason being that when I am in control, I can adjust the speed of entry and whatnot for my own comfort. You might also try a product made for lessening the discomfort of anal sex, there are many products on the market for such use.
It is always recommended to use condoms for any type of sexual interaction, but it is most important to change the condom after anal sex, before it comes in contact with ANY other part of your body. If you have anal sex and decide to switch to vaginal sex, your boyfriend must remove the used condom, and you can use a wipe to cleanse yourself, before starting vaginal sex.
If you find that you enjoy anal sex, you can do additional research to prepare yourselves for future encounters. It's wonderfully that you sought advice before attempting it, being informed is always beneficial. I hope this was helpful.
-I am not a medical professional, the above statements are based on y own experience with anal sex as a woman with a monogamous male partner.