Of course!
You are walking through them because your objects have no collision, this will be added in object maker. If you want to stand on them, first pick a simple mesh that has no collision (The one that you walked through). Now, go to 'object maker' and load that mesh. Go to the collision tab. Under collision type, you can load the following type you want. For example if your mesh is a tree or rock, 'Box' is recommended and you click add new. You can change the size of it as well by just using the scale.
Once you had added a collision and made it to what pleases you, go to object tab and click test.
You'll see that you cannot go through the object! And don't forget to save it.