Since the plan is to create four partitions, the best option after creating the boot partition as a primary partition, is to create the others as logical partitions. But before creating logical partitions, you first have to create an extended partition. If all this is foreign to you, read guide to disks and disk partitions in Linux.
To create an extended partition, select Extended Partition from the Create as dropdown menu. Specify the size for this partition, then click Add. Note: The target hard disk used for this tutorial is 300 GB in size. I chose to use just half of that for Linux Mint Debian. The other half I reserved for a possible dual-boot configuration with another distribution.
This is just to show the layout with the extended partition. Note that there are two unallocated partitions. One is under the extended partition, the other, is not. We will be working with the former. So select it and click the new button.
The first logical partition will be the root (or /) partition. All you need to specify here is the size. Because resizing a non-LVM partition is not a simple process, be generous here. For this test installation, I allocated 20 GB to it. That will be more than enough for an installation of Linux Mint Debian. Note that a new installation of the MATE/Cinnamon edition takes up about 6.3 GB of disk space. Add.
For the partition that will be mounted at /home, I allocated the bulk of the remaining disk space. Add.
Swap takes up what is left. For this partition, select linux-swap from the File system dropdown menu. Add.
Bact to the main GParted window, click the apply button to finalize the operation, the quit GParted.
That should bring you back to the main installer window. Click the Refresh button to see the new partitions.
This is what the window should look like after the refresh and after you have edited each partition to specify the mount point and file system type. To edit a partition, double-click on it, or right-click on it and select Edit. Finally, click on the Forward button to continue with the rest of the installation.
This is what the edit partition window look like. You just need to select the mount point and file system type for each partition. Note that ext4 was used for the file system type for all the partitions. It is not necessary to edit the Swap partition.
By default, the installer will offer to install GRUB, the boot loader, in the Master Boot Record (MBR) of the disk. If, as in this example, Linux Mint Debian is the only OS on the hard disk, the MBR is the proper place to install GRUB.