I'm going to remove a hwbb heater from my dining room to install a set of french doors, once I drain and reconnect the copper pipes in basement. What is the proper procedure to bleed the system

Note : I have a weil mcclein gold boiler

That is a huge question. Usually the auto fill valve on the incoming water line will take care of the refill and then you will need to bleed the system. Hto water systems are all a bit different so trying to be accurate is almost impossible without being there to see what you have to begin with.