You ease your dick in at first. Sometimes you have to guide it in with your hand, sometimes the foid helps you with it. You can do other things during the "guiding" part to ensure that your dick stays hard; playing with her nipples, kissing, etc
When your penis is comfortably inside the foid's orifice, one or both of you can establish a rhythm. Sometimes this means speeding up, but speed isn't necessarily everything. I personally like it when the whore is athletic enough to control her hips well, and is skilled enough to take into account the size and curvature of your dick, and angles her body and its motions accordingly to maximize friction. And sex is better when you respond to the foid's emotional cues and vice versa.