Did you work through the TurboCad Fundamentals? I think it comes with designer.
In paper space, you can orient how you want the page printed and bring in the margins from your printer set up.
For the line, if you really want to set an absolute line (which usually isn't what you want) you can single click on the line tool. Then shift-tab into the x of the xyz (probably just xy in designer) field and type your X dimension, then tab into the Y and set that one. Press enter, and then Shift tab again into the X box to set the X for the end of the line, and tab to finish off with the Y for the end of the line.