Hi there Amanda1. My son needed to wear glasses from 18 months and also a patch on one eye for four hours a day. To start with, we used bribery - one Smartie when the patch and glasses went on, and one Smartie when they came off. This worked really well. When he no longer needed patches, he realised that he saw so much better with glasses than without them that he always kept them on. Lots of people had suggested that we should build it up gradually, just an hour at a time to start with, and so on, but in my view this confused things, and he was much happier once he realised that this was a new thing, and here to stay.
By the way, always ask the hospital for two prescrptions so you can get a new pair made up quickly if they get broken (which happened to us all the time). You can get glasses with very flexible sides so even if the child pulls them off by pulling the arms out to the sides they bend but don't break.
Another tip - Specsavers don't charge a penny for children's glasses, where mnost places charge you for the frames.
Hope this helps - good luck