Like y'all the new photobucket cornfuzed the heck out of me. Tried Imgur but wasn't happy with that either as it's very slow to upload and edit. Went back to PB to see what I could do as I didn't want to re-upload all my pics to a new host.
Once your pics are uploaded in the new PB, select Edit at the top.....your gallery opens. One of the options is resize. Click the pic in mind and then enter the dimensions, then apply, then replace/save. This is the same thing you have to do in Imgur, but it takes far less time. Just my .02.
Test of a resize to 360 wide from the new PB: