Activating a Malwarebytes key is really simple, just follow those steps:    

1. Download the file from here: PC here, Mac here , Android here 
2. Once the Trial Version is installed, click on My Account on your screen. 
3. Put your Activation Code in.

Keep in mind that if you already had an existing Key in Malwarebytes you will need to click on Change License key in order to enter your new license key. 

The key is not working 

If you have activated the key according to the guide but the code appears not to work, please check what type of error message you receive and depending on it follow the appropriate instructions:

• My key is Duplicated / Already used
• My key is Invalid
• My key is region locked / can't be activated in my country
• My key activated a different product
• My key did not activate all of the content