As vinnywrite said, unless the disk (partition) is in the fstab file, you need to specify where to mount to.
/etc/fstab contains a list of definitions so that the kernel can mount them itself, or know where to mount them when requested.
To mount your partition temporarily, you'd do as above - create a place for it to mount in, then tell it to mount there explicitly.
You can try
mount -t auto /dev/sda1 /mnt/sda1
or replace auto with the filesystem if it doesn't autodetect.
If you want it to automount, or mount like you initially tried, look into adding an entry to the fstab file