Can't export in MP3 // Don't know how to put a beat in the master track

[Lucas5C33]

If someone can help, i dont know what to do, 

My multitrack looks like this, ''Principal'' mean ''Master'',

I also have another problem, when i put my Asio Driver on 44100 Hz with 32 bits, all the song and tracks will sizzle, i dont know why.

Hope y'all can help me out