Hi there!
So you are new with ETABS, I wish I had had someone to ask this kind of questions when I had just started. Therefore it is great to help others as I may.
If you are using ETABS 2013, whatever option of the above mentioned will be fine, except for the "mesh" option, meshing applies to shell elements and frame elements but it does not help you to draw a multi span beam.
Here is one option: Set the grid system including supports as grid lines. Then draw the line starting at the firs support and ending where the support is supposed to be, an continue on to the next supposed to be support grid, go on. Once you drew all the spans, assign supports by right clicking the points where you want each support and then going to assign→joint-restraint, now pick the type of support you need.
Hope it helps!