IF your first map is named differently, you can also open the app.lua script and lines 26,27,28 are where the first map is loaded.
--Load a map
local mapfile = System:GetProperty("map","Maps/start.map") --start.map is being loaded.
if Map:Load(mapfile)==false then return false end
You can change the start.map to what ever the map name is that you have or just resave your map as "start" and it should load up just fine.
("map","Maps/start.map") Maps refers to the folder that the map is in and start.map is the actual map name.
Over kill on the info but maybe it helps some one down the line. . . . .