Deleting "Catagory". Please Help!

Hello all.

I am very new to all this. On my opening page https://www.lamusicaesmiarma.com I am able to use the entire width for my blog. love it.
However on the page called “mensaje” There is a “Catagory” menu and a date menu. How do I elimate those so I can use the whole page?

Thanks a lot in advance.

Joshua