If you don't know any programming language at all, I'd suggest that you start with something other than assembly language. You need to know how to transfer your ability to solve problems to a rather strict paradigm. Once you have that, then you can move to the even stricter paradigm of the Von Neumann machine.
I would recommend Python. It is an interpreted language and you can get it free. You can enter simple statements at the command line, or you can write entire programs that run from the command line, or you can write programs that incorporate a complex GUI interface.