Yes, I stumbled onto the option to create a partition and fixed my own issue a few hours after asking this question.
For those that might get here via search:
- Open disc manager from the menu that pops up after pressing Win + X.
- Right click on the empty partition to the right of the disc name.
- From the menu, choose to create a simple partition.
- Now just follow the instructions. You can just keep clicking "Next" to create a partition with default settings.
If everything was done right, open File explorer and look under "This PC". It should show up there.