Greycat how do I do any of that?
I am having hard time maintaining control of world map generation as it is.
I can successful do channels so far and make the downstairs openings but I can't seem to figure out how to get my mining dwarves to keep digging down anywhere.
Once you have the downstairs on level, and the upstairs on the level right below it, you should be able to d->mine the squares adjacent to the upstairs on the lower level. Be careful to only designate areas that you want your miners to dig through, if you dig into a river or a lake, you will learn some stuff about !!FUN!! lol. This way you can designate your mining areas and your miners will get to it when they look for a job to do. Your miner must have mining labor enabled and have a pick, that shouldn't be a problem if you were able to connect the stairs. If you are waiting awhile for your miners to get to work, they may be asleep, or eating, or drinking, or doing another job that you can see in the "U"nit screen.
Once you mine out a large area underneath the surface, try making another set of stairs to go down another level, and dig a large area on that lower level. It is a good way to get familiar with what things look like underground, and while your miners work, practice changing z-levels with the < and the > keys, and F1 to center on wagon if you get lost. Press TAB a lot to browse the command menu, and watch the minimap.
Keep it up, and the rewards will be great. Welcome to the game!
About stairs, downstairs must be designated on top of the level that the upstairs is designated. Without the upstairs, your dwarves will not have access to the lower level. Once you get the connected stairs, you should be able to dig anyway on that lower level that you see fit.