It was really easy, but I had a little bit fearful about the fees. You can do the process in two o three steps no more. Everything is quite well implemented. 

I hope this can help you

1st Step

Go to uphold account, to the activity tab. From here, you can see your balance.

On the right side, you will see a form. Fill the from field with the ETH token and write down the amount to convert. Select the currency in the second field, and finally select on the to field the destination token, BAT in this case. You will see the conversion and the fee which is zero in this case. After that, click on the preview button for seeing the resume.

The final step is when you confirm or not the operation. Only remains to confirm o cancel it. 

If you confirm the conversion you will have automatically the new token in your activity tab.

Really easy!!! :) 

I hope this post helps you!