There are 2 main ways to get citations into MyEndnoteWeb: one is to is to hand-enter them yourself; the other is to import them from one of the research databases.
There is a Firefox toolbar you can install to assist in importing citations and some Chrome & Safari Extensions as well.
Importing from databases
Many library subscription databases available through the web can export citations either directly into EndnoteWeb or indirectly, by exporting a citation file that you then upload into Endnote web.
Exporting Directly from a Database into MyEndnoteWeb
Exporting to a File and Uploading to EndnoteWeb
Some database products don't have a direct export-to-EndnoteWeb option. For them, you will need to Export a list of your citations and Import them into Endnote web. If you use the Mozilla Toolbar for Endnote Web, the process skips a few steps.
Summon is currently one of those databases.