For those with partners willing to receive anal, it is important to understand what is and isn't acceptable with anal play, and what to do when it comes down to doing it. Each person is different, and what one person may love during anal sex could be very different to what another may like. You will need to communicate with your partner to find out what works for both of you, while also ensuring you both still have a great time.
With any type of anal play, you will need to use lube. While condoms do have their own already, it is best to use more. There are so many different types of lubricants available that there is bound to be something suitable you can use. If you aren't sure how much to use, there should be instructions on the packet, but as a rule of thumb it is best to have too much and not too little. Anal play without plenty of lubrication can not only be uncomfortable but also painful, which can really ruin the mood.
Another thing to keep in mind is that going from the ass to the vagina can transfer bacteria and cause an infection, so if you feel the need to do this, change the condom first. Your lady will appreciate it and you'll both have a better time because of it.
If your partner hasn't tried anal before, take your time. Don't try to dive straight in there. Instead, get them nice and relaxed, maybe with a massage, and pay special attention to their bum. Use some lube and try just playing with their ass before slipping the tip of your finger in. If they don't enjoy the feeling or want to stop, listen to them. If they want to continue, try moving your finger a tiny bit by wiggling it, and very slowly see if you can slide further in. Over time they will be able to relax enough to allow your penis to slide in, giving you a nice tight sensation.