I've got an InfoPath form and when I click to add an item it gives me the 'Save' option.
How would I change it to submit? Or would I need to get the URL of the InfoPath form and paste that link to a SP page for it to open with a 'Submit' option?
You can a Button and Rename it as Save and write the rules you want.
If you want to change the button configuration you can go to option and change button visibility.
And again if you want to disable the submit button; Go to Data Tab -> Submit Options -> untick Allow Users to submit this form.
Personally I disable the ribbon and add buttons to my forms. People tend to look at the bottom of form they just filled out, then go back to the top but that's personal preference.