We usually have two people begin the process of introducing cross ties. If your baby stands in his stall and stops fighting when pressure is applied to his pole if he pulls back that is a very good start.
To begin with lead your horse in to the crosstie and have someone hold him and go about your activities, brushing, hoof picking etc. After the horse stands quietly for that, you can attach the crossties. Make sure that they are quick-release by the nose, with zipties or something else making them “breakable” at the wall. Once again, a helper can stand by their head, with lead rope attached while you brush, fuss, etc.
The last step is to attach crossties and leave the leadrope on your horse while you work on him by yourself, always ready to support with the leadrope if he gets worried. This is usually a process I do over a couple of weeks unless the horse is super easy or worried… then we adjust our timing.
Quick visits at first with lots of praise are a good start to get a horse very comfortable in a place they will likely spend quite a bit of time in the future.