Real making a turn-based strategy game in construct is very advance in terms of knowledge of the program.
There's a good chance that you are going to have to build the the engine for the game from scratch.
You are going to need to now pathfinding algorithm like A*(pronounced "A star"), Dijkstra, Heuristic, and apply them the accordingly to movement range,and cost of terrain on the map.
This is hard just from the player aspect of the game play.
Now for the enemy NPCs It gets a lot harder.
Enemy NPCs pathfinding condition are always changing based on players movements.
when player gets to a certain spot the NPCs move to closet player character.
As it get closer it and more character are made available to the NPCs pathfinding condition may changes again to compensate for that.
Not to mention the the stats, items and other thing that make these games great.
Well as for turn-based strategy game, demo, or tutorial there are none at the moment.
I hope to change that with my TBS I got in the works.
Anyway like Lucid said.
learn the basics. try your turnbased ideas a little, and then ask more specific questions if you run into trouble