The problem is that the single partition is set to the partition size of the original disk (and any pre-partition information, such as boot loaders, are also copied across) so the cloned-to disk is mirroring what was on the cloned-from disk.
I’m assuming you are using windows, if so you’ll need to go into the disk setup… and create another partition if you want to use the additional space (https://www.lifewire.com/how-to-open-disk-management-2626080).
That said, my personal choice would be to extend the current windows partition to be as large as the whole disk (were I using windows instead of linux. Linux introduces the possibility of doing partitioning so much differently). To do that, you will need software that can re-size a partition that you boot up from external media (usb/dvd) and then follow the instructions/guidance. For a fairly simple, but more than usable, bit of software I’d recommend gparted which is free (basically its a minimal linux with a gparted front end) https://gparted.org/download.php For instructions on how to use it see - https://gparted.org/display-doc.php?name=help-manual
One thing gparted seems to omit from its instructions is how to install it to media… basically its an iso file that needs to be written to a USB stick, or a DVD/CD, using your favourite burning software.
Final word of warning, it might all go horribly wrong (its rare, but you never know when a power cut or some such might happen halfway through extending a partition). Make sure you have a backup (although assuming you’ve done nothing with your original disk, worse comes to the worst just re-clone and start again).