Select the block
Ctrl-V for Visual Block mode
This will allow you to work with columns and rows. For example, you can insert new characters to the beginning of a set of new lines (think adding indentation, comment # symbols, etc)
} for paragraph (or G to end of file, etc)
Insert the new characters (or delete etc)
Shift + i to Insert
(this will only display changes to the first line as you type)
Esc (exit Insert mode) this will then apply your edit to all lines in your selected block