There is a guide on how to use the Classic Guild Bank addon, on the addon page: https://www.curseforge.com/wow/addons/classic-guild-bank
Although it looks like it might be broken atm?
It's been working for me all this time. I don't think I ever downloaded that Jan 12th update. I believe I am still using the Dec 26th version of the addon. You can see the past versions in the Files tab on their curseforge page that Poisonenvy linked. When you are logged into a character and have your bags/bank open, you can type /cgb and it will give you an export string. You take that string and paste it into the Import on ClassicGuildBank.
Guild Launch Profiler should already be up and working for Classic. The main thing is that ClassicGuildBank has extensive and incredibly useful features specifically for guild banks.