You can't debug until your code compiles cleanly: it isn't until then that an EXE file is generated, and you need one of those in order to run your application, either directly or within the debugger.
What you have are syntax errors - and quite a few logic and typing errors - which you need to fix before you can go any further.
Start by looking at the "Errors" pane, and read the first one carefully, then double click it - that will take you to the line it found the problem on. The message you read will describe the problem, and is generally pretty accurate and useful. It's probably complaining about this line (among others):
If chk L Then
Which is pretty much meaningless as is: "chk L" is not a condition at all; it can't be "resolved" to a "yes or no" answer. Did you mean "is chk the same as L"?, or "is chk greater than L?", or what - we have no idea and - to be brutally honest - from the rest of the code it doesn't look like you do either!
DO yourself a favour, and start again: read your homework question carefully, and think about what it want's you to do before trying it manually on paper. Then start working out what you need to do i order to move that to a computer - just jumping straight into code is a big mistake and will waste a whole load more time than you will save!
If you are having problems getting started at all, then this may help: How to Write Code to Solve a Problem, A Beginner's Guide