If you use this lotion it will moisturize your skin so that it’s firm and soft.
Because the hiragana ends with an う sound, you know this word is a verb. The kanji itself means watered. When something is watered, it is moist and damp. That's why this verb is to be moist or to be damp or to be watered.
If you get moist and damp, then you're all (うるお) wet. It's just how it is.