Question 1 : how do i add the apps to the main page beside the homebrew channel etc ?
Depending on the application you can get a forwarder channel or you can make your own although on both a bad wad file can brick your system menu.
Question 2 : do i need specified software to play new super mario ?
There are numerous threads regarding NSMB which are more indepth about the how to get it working with different loaders and types of images. Use the search function to find some of the threads.