Platform collision troubles

I am creating this game that requires that platforms are used to reach a goal at the top of the screen. i have all the needed components to make the character move but annoyingly i cannot figure out how to make the characters collide with the platforms and stay put on said platform. Does anyone know how to fix this problem.

Start here, while the other Power Users sleep?

Welcome Matthew.

Creating Animated Apps describes how to use Sprite collisions of your characters.

Here is a game that probably does some of what you want to do that you can use as an example (look upOh My Spikes – Create a game from scratch using App Inventor on in the Tutorials section of the site.

Also I’m making a 2D platformer (How do you make a Ball or Sprite 'jump'?) - #24 by SteveJG