The first thing is to make sure that the partition you think is the correct one. We do this by creating a mounting point, for example, within /media:
then, mount the partition there:
mount -t vfat /dev/sda5 /media/data
Once you check this is correct, you make it permanent, by opening Kate from the terminal window as root, and opening the file /etc/fstab. Add the following line at the end
dev/sda5 /media/data vfat rw,umask=0000,uid=500,gid=rau 0 0
where uid and gid are the User ID and Group ID, that you can check opening Users and Groups from the start menu.