Just start off slow by fingering and place a hand on her stomach above her va ja jay,
start fingering her faster with more fingers and stimulate the clit while doing that ,then try to reach a soft area inside her va jay jay and massage it with one finger, while you keep fingering her fast. keep doing that until she squirts..
here is a link that you can read, that's how I found out about this! not that I have tried or anything..
According to the Planned Parenthood website, only 1 in 10 women squirt during orgasm. For those that have the ability, it's thought to come from stimulating the G-spot, however it's not known if all women have a G-spot, or if they do, whether all women can orgasm from G-spot stimulation. So while you can try, realize it's rare - most women orgasm without squirting, and orgasm from primarily clitoral stimulation. Whether a woman could be trained to squirt is probably not known - surprisingly, our understanding of female sexuality is still quite rudimentary as sex research is difficult to conduct and difficult to fund.