With MBR alias MSDOS partition table you can have only 4 primary partitions.One of them could be an extended partition, which is a container for logical partitions, so that you can have more than 4 partitions.
You have 4 partitions already, and one of them is an extended partition. I think you can have only one extended partition.
So you should increase the size of this extended partition to include all unallocated drive space, Then you can create logical partitions inside it.
gparted is a good tool for these tasks, but you must swap off in order to remove the lock.
Please backup everything that you cannot afford to lose, because editing partitions is risky.
It is a good idea to boot from another drive in order to edit partitions, for example from an Ubuntu live USB drive.