How do I add a file to my model in the Modelling Commons?

[Wade Schuette]

Today I uploaded my first model to the Modelling commons, successfully,  but when I select the model and go to the FILES tab, and enter the name of a file ("input.txt"),  I can't upload it because it complains that there is no file-type entered, but it has no drop-down list of types to select from, and it won't let the cursor go into that field so I cannot type "txt".  How am I supposed to do this?  Thank you!