Thats just the keyboard controls. The mouse is used to control units and target spells. Mana comes from manafounts and your altar. You can build manaliths over manafounts to transport man to manahoars, small armless beasts that follow you supplying your mana. Your altar cannot be destroyed unless it is desecrated.
All units have souls, minus wizards.
When one of your creatures dies, it drops a blue soul, you can just run over these to pick them up. If an enemy creature dies, it drops a red soul. These must be convereted and sacrificed at your altar. When you or near an enemy altar, you can sacrifice one of your living creatures to desecrate an enemy altar. Once you kill the enemy wizard while his altar is desecrated he is banished forever.