Being new here, let me help in giving you some suggestions. You ask a question about having a problem trying to enter the "code". It sure would help if you provided some details in just what the issue is. Like what frequency are you trying to enter? What is the "code" that your trying to tell us that is giving you the error?
The details are what we use to try and help you resolve your problem.
We all have been in your shoes at some point in our learning curve. I would suggest trying to slow down and really think about just what your trying to say to us. is there enough information being provided so that an answer can be provided?
I always try to stand back and read what I have typed to see if I have managed to get my thoughts down in the message so that others have a clue as to what I am trying to say. It's a learning curve that takes years to learn. Having been in this field for many many years, I still on occasion seem to blow what I am trying to say. So don't feel bad being new to the scanner field. All of us had to start some where in the radio field.