Other adding slice(?) question

I have legacy WinXP and FreeBSD-10.3 on the same physical disc. Now I am trying to add disc space to FreeBSD OS, so I've resized NTFS disc "D:" and freed space after it under Windows ( gpart shows it's to be free).
What now I should do? "17.3. Resizing and Growing Disks" in Handbook says only about gpart, but somewhere else I saw newfs mentioning. Should I just gpart add -t freebsd-ufs -a 4k ada0 and add a line in /etc/fstab or there's need for some other steps?
Thank you. Was not sure for that. (Could have tried but knowing in advance is better.) )