How to present my worksheet in more readable and understandable view, not in the view of commands?

I am a newbie in Maple.

I am trying to evaluate and to display the electric field with Maple in Document Mode.

I have several questions:

1. How to delete errors from prevous calculations?

2. How to delete formuls from previous calculations?

3. How to wirite vector functions?

4. How to evaluate vector funcitons?

5. How to display 3D plot of a funciton?...