I have an 8 year old autistic child who is in pull-ups and I need help with potty training.?

My child knows (most of the time) when its time to go. I just need help with getting comfortable in the bathroom on the toilet. The child will sit for a few minutes but then hops up and wants a pull-up on to do whatever needs to be done be it number 1 or 2. Can anyone help please. I know it depends on wether the child is ready but is there a way to interest them in trying? I had a family member recommend stickers or favorite food or snack to entice them in sitting but is there anything else?