I don't have access to Step 7, so cannot be sure on the buttons.
For Symbolic programming, I believe you right click on the folder that contains the blocks and select properties. The last tab shows the programming priority selections, it will have 4 squares, each with a click point in, the default is the top left (address priority), I always change to the bottom right (symbolic priority).
Once you have done that, it means that when you regen, the addresses will follow the symbol.
So now you could go to the symbol table and change the DB address, but then you would have to re-gen (or go to every instance of the DB usage).
I'm not sure what the official name of the regen function is, I do know you get to it from the the top drop down menu's. Its a function that shows the code in its structure and highlights any errors in the blocks, within that there's the regen option, do the regen and the code will be updated.
Save and download.
Of course you woluld have to be carefull downloading, it would be better with the process stopped, as the code will download errors may occur in the PLC if running.
Hopefully someone else who knows what I am talking about here will read the thread and correct anything. Its useful to know this especially, if like me when coding in S7, you use a lot of UDT's.