Firstly, ask what exactly your partner wants. If you’re not sure where to start, maybe discussing various scenarios with them is a good way to start. This way you can find out what they are most likely to respond positively too.
Start slowly, try out a few words and phrases and see how it goes. Don’t pressure yourself to be perfect straight away, it might take a few attempts before you find the perfect words and scenarios to satisfy you both. However, if you are not comfortable with humiliating your partner, you can say no. We all have our limits and the tops and Doms have as much right to say no to doing something as the subs do.