As your as your current visa (Bridging Visa B, 487, 489 or 475) which allows you to travel overseas, you can travel without filling in or submitting any forms.
If you are currently on Bridging Visa A, you will need to apply for and get granted Bridging Visa B before you can travel.
Please note that for 887 to be granted, you must be residing on shore. Generally Case Officer will let you know if the decision on your visa is imminent and you are not in Australia. Unless really desired, all travels while your application is pending must be avoided and deferred.