Riding my man

I love riding! But I normally lay down my head next to his and do the work with my legs however I would love to sit up and do it but I honestly don't know how it works 😂 his my only partner for 2 years and he keeps asking me to and I'm like how? Please someone give me a step by step idea of how to do it as this is stopping us from having sex anywhere else (sofa) (chair) etc . Anyone who helps is such a life saver 😂 Tia