Hey
@sip1684!
If no one has already helped you in-game with this, you can actually grab the water or fire in any order! After you fill your bucket there will be a spot you can use it on. After you click that spot, the bucket will become empty and you can then fill it with the water.
I hope this helps/clarifies your question! If you have any other issues or questions feel free to ask here on forums or create a ticket in-game by doing /t create to get an online staff member’s help. Have a wonderful day!