For many it's just a matter of relaxing and usually a combination of g-spot stimulation and deep pelvic massage. There is nothing biologically different necessary for someone to be able to squirt, everyone is capable of it. Being well hydrated helps as does feeling you're in a safe comfortable place to experience it.
If you're looking for a more hands on thorough explanation, I've heard good things about this author and book, perhaps that could provide more assistance. https://www.amazon.com/dp/0997085002/ref=cm_sw_r_cp_apa_fabc_Kqw0FbY4299NR