Written by Emily Nagoski, Ph.D.
"Hey there, lustbucket of my heart, would you be interested in making me ejaculate?" is a good start.
I'm going to assume, maybe inaccurately, that you have never ejaculated before. If that's the case, be aware that not all women can ejaculate, in fact, a reported 10-52% of women experience ejaculation at some point in their lives,1 and there's no reliable science that I know of to tell us who does and who doesn't. I have a friend who never ejaculated in her life until she got past menopause, and then she started ejaculating all the time!
But it's fun to experiment and try new things. You can present the possibility to your partner in those terms, the same way you'd introduce a new toy, new lingerie, a new position, handcuffs, blindfolds or an additional playmate: Gently ask for permission, and be ready to hear no.
Now, how to ejaculate. The general rule of thumb for ejaculation is that you need intense, prolonged G-spot stimulation. So, after you're already very aroused, penetrate your vagina with fingers or a glass toy or something similar, so that you can get some firm pressure. You don't need deep penetration, only a couple inches, maybe two knuckles' worth, but you need firm pressure on the anterior wall (that's the top, the side closer to your belly button) of the vagina. That's where your G-spot is.
You also need abundant time. Like, half an hour or an hour. Ejaculation typically requires a long, gradual build up of sexual tension, so only try this when you've got some free time on your hands. A not-so-lazy Saturday afternoon is perfect.
Prolonged intense stimulation like that can be hard work, not to mention potentially irritating, numbing or painful. Take breaks, do other things.
Finally, don't take the whole ejaculation thing too seriously. Some women do it, some women don't, some women do under some circumstances but not others. It's a fun thing to play around with, but it doesn't make your sexuality any better or worse.
Enjoy the sex you share with your partner, without getting too goal-oriented.
1. Pastor, Z., & Chmel, R. (2018). Differential diagnostics of female “sexual” fluids: a narrative review. International Urogynecology Journal, 29(5), 621-629.