How do I enable javascript?

I'm filling out an appcation for a study permit in canada. My university website said that i should download adobe acrobat reader and use it to open the application pdf. I didn't want to pay for adobe, so i opened it with firefox instead. In the document, there are tab selections that it allows so you can select answers accurate to you and fill out the document. But at the top of the document it says I should enable javascript by going to preferences, then edit, and and then reopen the form. How can I enable javascript in firefox? I'm having difficulty finding the preferences and edit sections.