Short Application Form modifications

Summary

Where do I make changes and will it break anything?

Content

Hello all!

Need to make a few mods to the short application form and have never done it before.  First question: where the heck is it? I have looked several places and have no idea where it is.  Second question: is there anything I need to consider or do before making a change/  Will it affect anything 'in process'?  Will it potentially break anything? etc... 

Thanks!

Jenn