FIrst start by going to the front of the yellow house.Now Head towards the pile of firewood in the corner.
Now walk onto the planks of wood on top of the pile of firewood. You may have to jump a few times to get over the invisable path.
once you reach the top you can get over the fence.
On the other side of the fence you can now reach the paths leading to the top of the houses.
There is a jumppad on the pile of dirt that will take you to the top of the house between the yellow and blue.
Once on top of the middle house you can head towards the edge of the roof and there is a pallet and planks of wood that have a invisable path you can use to get on the yellow house.
You can see the invisable paths I have makred in the screenshots to see what I am trying to explain.
Now you are free to explore the top of the yellow house.

Have Fun :)