Sweetheart, IGNORE all that 'advice' about using spit, very bad sexual health advice.
Have a relaxing warm bath with your man and take time to relax and get in the mood
Have plenty of foreplay to relax even more and use plenty of water based lube around the arse
When you are fully relaxed put a correctly fitting condom on his cock and smother it in water based lube and get him to put more water based lube around your arse
Now you should be ready to roll,
ensure that he is laying on his back, you can then straddle him and position yourself over his cock
together put the cock on target (your ring piece) and the YOU can slide down onto his cock taking your time. This way, you will also be able to move around more easily into a comfortable position, when you are sure you are comfortable and not in any pain you are start to slowly ride the cock.
You will have to add more water based lube at some point to (1) ensure that the condom does not get damaged and (2) that you get a smooth ride.
Some guys like to douche before sex, whilst this makes you clean inside, it also remove the natural lubrication from within and dries the lining of the arse out thus making it fragile and prone to tearing. Your arse might tear anyway as you are a virgin and at other times. If this happens, stop fucking and if there is lots of blood see the ER doctor.
Anal sex can be great fun, but it is not for everybody. I've forgotten the last time I had a cock up my arse, I just find it too uncomfortable so don't worry if it's not for you, there are plenty of other things we can do that are enjoyable
Brinz