It costs armaments of the same type to expand troops to a higher level. You use the Munitions Factory to produce the armament of your choice. 

First be sure to load troops into Army/Air/Navy base and then click on the "Troop List" tab to select any que up any troops and select the "Expand." tab. Now select the desired troop or troops!

Be sure to uncheck the "auto dispatch" selection if you do not wish to have any troops automatically dispatched when under attack. Otherwise keep the box checked! 

If you have any damaged troops, be sure to refill them before expanding them. 

Note that you unlock the expand function by leveling all bases to lvl 3. 

if you found this information helpful then that is great, and if you have any other questions then feel free to contact us!