Amending Bylaws - What are the Steps?

All knowing brownstoners, I need your help with something. We have a verbal agreement with one of the other major shareholders in our building that we can obtain exclusive roof rights. We want it to be done properly and go through the proper channels. I know that the bylaws will need to be amended to remove the roof from the common areas section. What is the process for doing this and who has to give approval of the amended documents?

Does anybody know of a good attorney that I can reach out to?

Thanks.