Anywhere in the same server where SuiteCRM is installed. Better if it’s not in the same folder, because the script is not password protected. To enhance security you may change the name of the script to make it impossible to be found. You may even set up a password with .htaccess and .htpasswd (but it requires technical knowledge)
Exactly!
If you change the name of the file or place it in a different folder you have to modify the way you invoke the script accordingly
The script presents you with a big table listing all your campaigns.
At the top you can reset for immediate sending irregardless of campaigns. Similarly you can suspend the sending. This can be done for all emails in the queue or just predefined numbers (10, 25 or 50).

If you want you can do it selectively by clicking on one of the links for one single campaign:

If you click 3 times reset 50 emails for a specific campaign you will reset 150 emails.
The suspend links suspends the emails for 24 hours from the moment you click.
If instead of the options All, 10, 25 or 50, you want to put a different number, you may do so by copying the link (instead of clicking it), then paste it to the browser address bar and modify the value after either block_n (which suspends) or reset_n (sets for immediate sending).
For a specific campaign (note the campaign_id variable at the end):


For a specific campaign (note there is no campaign_id variable at the end):


Yes, that’s all you have to do to set it up: just enter the appropriate values.
You may have noticed that there is a number inside brackets for each link. This number is the actual number of emails that is going to be reset. So, for example if you click on “reset 50 (32)” this means that there are only 32 emails in the queue for that specific campaign that may have to be reset.