Make sure you plan to meet a friend or do something distracting the first time you drop them off (and potentially the second time too). This will help you as often it's more tough on the mum!
Try not to judge the first few weeks. It takes them a little while to adjust but one day they will. It is so hard in the first few weeks to think you are doing the wrong thing but give it time. Mine hated the first couple of weeks and was upset and drop off and pick up; then one day I went and she was happy at pick up and she has loved it ever since.
I would try a couple of hours then 4, 6, 8 if you’re able to gradually increase.