Towny has a useful GUI (Menu) you can access with "/tgui". In this menu, you'll have access to almost all of the usual Towny functions by clicking on the appropriate icons. For example, you can toggle the Plot Map on/off by clicking the "Resident" icon, then the "Toggle" icon, and finally the "Map" icon.
Some of these functions require input, such as creating a new Town and giving it a name. Simply type the input into chat and it will apply to the function you're using. For example, when purchasing Bonus Townblocks under the "Town" icon, you'll have to specify how many you'd like to buy. Simply type that number into chat and you will purchase that number of Townblocks.