To auto-mount a partition during startup, you have to add a new entry in your /etc/fstab file.
sudo nano /etc/fstab
Just follow the format of an existing entry.
# <file system> <mount point> <type> <options> <dump> <pass>
To identify the UUID of a device, just issue the command:
The important thing to take note here is the mount point and the type. The mount point is a directory in your system where you want the partition to be made available.
For example, I set it to /mnt/ext
This means, if I want to access the contents of that partition, all I have to do is go to the /mnt/ext directory, assuming the directory is existing.
The type is basically the file system of the partition.