My plugins are not working

Hello,
I just want to know why my plugins do not work every time I try to install them or using them. I had to do it manually in order to install a plugin but it is not working. Could it be because I am using a free webhost? I am using a one called 000webhost because I am quite new using wordpress and I am learning how to install them and style them.
Another thing is that first I install wordpress using mamp, where I styled the page the way I wanted to look., the theme was 2011, and then I uploaded it to the server through a new wordpress file with the theme styled. Everything looks good but I just have that small problem.
This is the page: http://wrdpress2.herobo.com/
Help please