A regular dildo is not good for anal, not only because the size may be too much for a beginner, but also because there's a risk of inserting it too deep, not being able to take it out... and possibly ending up having to make an embarrassing visit to the hospital, lol. So if you can, buy a beginner butt plug set with plugs of different sizes to practice, since their shape is designed specifically for anal and to avoid accidents. They're also very kinky, and can be left "on" for a while. If buying them is not a possibility, practice with your fingers.
Every time you do anal, start slowly dilating yourself with small toys/just one finger. You'll eventually get better at it, and you'll be able to take bigger stuff, but don't rush it, you always have to start slowly, even when you're already an "expert". Always take your time.
And as you have already been told, hygiene is also very important. A enema bulb douche is more than enough to clean yourself. It's not good to use too much water, neither is doing enemas too frequently. The water must be lukewarm, neither too cold nor too hot. In any case, NEVER expect anal sex to be 100% clean.
Always use good lube. Don't improvise with moisturizer cream or something like that if you run out of lube.
