I am new to this. I have been creating flyers/posters on PSE and sizing has always been easy. I want to switch over to ID but cannot figure out how to create an 11x17 poster. I don't understand 55p0 or 66p0 and how to convert that to inches. Can anyone explain? Thanks.
You can pick the Tabloid preset from the page size dropdown, type the dimensions, including the units, into the various fields and ID will convert them to the current default ruler units, or with no files open open the prefs and change the ruler units to inches or something else you do understand and that will be the new default.
Program comes with help files http://helpx.adobe.com/indesign/using/create-new-documents.html
Suggest reading up - hope that helps!