Basically you just add a jump value to the player Z position which you decrease every tick by some gravity value. Then increase the gravity by some factor once you're falling again (for a better less floaty feel).
Of course you need to implement checks to see if the player is on ground. This has to be your own event logic. Check for overlaps and compare Z top positions of your geometry to the player bottom position (feet if you will) and also player top for colliding above when jumping - alternatively you could also use ray picking for this which will probably run faster but might introduce some other difficulties.
In general using some kind of state machine (via the plugin of the same name is pretty handy) helps in such endeavors.
If you want to I can still take a look at your capx file, sure.