You can reinstall, and select guided, use entire disk. Or you can
reinstall and select manual install, and then remove the exisitng
partitions, and then tell it to repartition and reformat the disk.

I do not know of a utility that will let you expand the exisitng
partions. Though there may well be such an animal for Linux. (I'm
fairly new at Linux, but I have done dozens of installs recently.
(Some because I am new and managed to get myself in a corner that I
did not know how to get out of.)