If you have never done any interferometry before, or if you do not know what is a uv table, we (strongly) suggest you read Sections 4.2, 5 and 6 before doing anything at all. These sections are short enough to give you the basic tools ( HELP plus the 5 main commands: READ, UV_MAP, CLEAN, VIEW and WRITE), and will give you hints on why IMAGER behaves like this.
Remember two things: look at the results (command VIEW) at all steps, and ask more experienced users whether these results make sense if any doubt arise.