Assuming that there's nothing serious going on (is there?), you can simply use dampened paper/cloth towels, as Car2ner suggests, or buy unscented, disposable baby/dog wipes. I had IWs for years and the breed is notorious for what people in the breed called "hairy" body parts. So, I quickly learned to do and maintain the sanitary clip that Sunsilver described. It's not complicated, just clip the hair around the anus, vulva and/or penis very, very short. Do make sure to buy and use scissors with blunt/rounded tips so that you don't create other problems.
ETA: If you've not done this before, consider tying her to a post or something, so that she doesn't scrabble off. Assemble ALL of your supplies before you start (before you tether her, in fact). Take a deep breath, smile, go slow, speak calmly and happily, and liberally dispense treats. She may be startled by this, but if you act like it's no big deal, she's likely to settle down quickly. The first time cleaning a dog like this, I like to stop before the dog gets too uncomfortable. Unless it's a hunking mess, you can come back in a couple of days and finish things up. That said, I'd suggest you come back in a couple of days and clean her again, anyway, cause I think it's a good idea to get dogs used to handling.
Last edited by Aly; 10-25-2017 at 10:40 AM.