If you want to look like Mario, you will need to download and apply Mario skin, you can become Luigi as well - its just a small hint to make everything look more authentic. It is way better to see characters from the original game running around, than just a regular Steve.
How to install maps:
- Download .mcworld file below
- Open file using any file manager to import it into Minecraft PE
- Open Minecraft Pocket Edition and look for the map among your worlds
- In order to install Resource pack, import it into the game and apply in the world settings