When i download a theme as a crx it downloads to my computer and doesnt install as a theme please help/:.

What is the version of Chrome that you are running?
Go to the Wrench and select About Google Chrome

What is the version of Operating System that you are running?

If a theme downloads without installing you can either, click on the file in the download bar, open the folder its in and double click the file (if you do and it doesnt open with chrome then right click the file and pick Open With and choose chrome), or open the folder its in and drag the file on to chrome.