Offer food a couple times a day. Maybe one cricket. Drop the cricket in the tank and walk away so you don’t spook him. Eventually the fish will start to associate you with food and be right at the top of the tank begging for food. That’s the time to pellet train. Right now you just want to get it to eat. Make sure all uneaten crickets are removed. I would even keep the lights off for a few days to calm the fish down.