AFAIK on Windows the physical disk containing the partition needs to be marked offline in Disk Management, and the disk or a partition given exclusively to VirtualBox running as administrator, otherwise access is limited to read-only
I would suggest checking some other sources as well, just in case this has changed over the years. If you do successfully pass the physical partition into VirtualBox read-write, you might need to set up a virtual disk with grub to boot into your physical Linux partition