The easiest place to start is to follow that link above and go to the "Watch Videos" tab. Occasionally near the top of the page there will be videos that offer up to five credits each if you click on a green box.
Then there might be a black box where all you have to do is start the video in the box. Wait until a small red box pops up at the top right of the video,; that should happen 1 second to 1 minute into the video. That red box is the sign you get the credits offered for that particular video. Usually 1-3 credits each. Click on the red box and move on to the next video. When the top of the box displays "Done!", refresh the page and the credits should then be added to your total.
Below that is are the videos offering usually 2 credits each. Click on each pink box and wait for the video to complete.
The next two things on that page involve accumulating views you cash in for credits. 100 views gets you 75 credits.
At the bottom is the carousel. Collect 1 view each for the 7 rotating boxes. Below them is a box to earn more views. Sometimes views are there, sometimes not. You can wind up getting anywhere from 7 to 200 views a day since you live in the USA and WGT has more access to advertisers here.
Surveys are a good way to accumulate credits as well. Do not do any survey that asks for any personally identifiable information, be it an email or your name, address, etc. Don't give them anything that leads back to you specifically. Be aware that you are on your own, though, since you will receive no support from WGT with regards to surveys. They can be extremely frustrating and some companies will lead you on, having you answer 25-30 minutes worth of questions only to give you nothing in return.
I've been here over 7 years and supported myself this way. Never entered a credit card anywhere. Never did an offer that required one. I quit keeping track of how many credits accumulated when I went by $750.00 worth in year 4.
Just be patient and flexible. Some days, weeks, months are better than others for accumulating "free" credits. Just be aware that they require a huge time investment as opposed to investing money. They are not really "free".