If she wants to help him, she should have her legs spread wide and she should reach back and spread her own ass with both hands. Then the lube and then PERHAPS he can get his dick where it belongs - balls deep in her ass.
to kisi365 :A man's anus and a woman's anus is not different lol. Even the feeling is same ( but it depends on the person) It is because they clean it. Usually enemas but there is another trick. You put something long inside and it come out dirty, you wash it and put again until it comes out clean. If you use lube with good smell or coconut oil with lube ( do not use oil if you are going to use condoms) it will smell good too. Just search how to do anal sex. There are more things you should know before you start doing it.
to kisi365 :Movie magic. The actors in porn take enemas, multiple enemas. That is why. And if a little something happens, they stop and do it again. You did not ask but muscle relaxants are used.