Use miniTool Partition Wizard or Easeus Partition Master to delete existing partition(s).
Right click partition for options.
When all Unallocated, create new partition.
Usually, USB sticks are FAT32 and only a single partition each.
If the stick is only to be used on PCs (and not in cameras, PVRs, TVs etc) you can use NTFS instead of FAT32.