I have been spending the last few days doing some Revit Structure training and one of the first issues I have seen come up is when working with some of the compatible analysis software. The installation, setup and workflow for each analysis software takes a small bit of time to work out.
If you have been able to get the ETABS link installed correctly you may notice in some cases that the option "Send Model to ETABS" (Tools>>External Tools) is greyed out. If this sounds familiar to you then chances are you may be trying to send to ETABS from an active view that Revit Structure does not like. Change your view to one of the following and you should be able to send your analytical model to ETABS.
The following active views work in Revit Structure 2:
Structural Plans, 3D Views - both the structure and analytical model, Elevations (Building Elevation), Elevations (Interior Elevation), Detail Views (Detail) , Drafting Views (Detail)
The following active views grey out the Send to ETABS option:
Graphical Column Schedules, Sections (Building Section), Sections (Wall Section), Legends Schedules/Quantities, Sheets (All)