One simple way is to:

1st remove the MS-Windows boot from your grub boot menu.

Then 2nd, create a mount point (directory) with appropriate permissions under /home/your-user-name/data
(ie call it directory 'data' under your main user home - assuming you have only one user who needs to access the extra/new space).

Then 3rd, reformat the MS-Windows file format to a Linux ext3 format (which wipes everything on that partition).

And then 4th edit your /etc/fstab file to mount the new ext3 partition under /home/your-user-name/data.

And then 5th, reboot.