To make the platforms for your game search "platform sprite" or add a term in front like "graveyard platform sprite" or "cave platform sprite". Put the sprite through the background remover.
Upload it as a sprite in your game and hide it. Use the select tool and draw a box around the sprite you want to add toy your game. CTRL+C to copy it, switch to your ground sprite, and CTRL+V to paste it. You can move it where you want and also paste multiple times. Anything you put on the ground sprite is solid and your character can't go through it.
You need to create 5 levels for your character to get through. It should look like this when you are done. Everything you add will be a solid object (no collectables here).
Your end goal for each level is going to be its own sprite. The code on that sprite is just to move it around on each level and will look like this. The X and Y coordinates will be where you want it to show up on each level.
This code needs to be added to the touching stuff block.