As you likely know, we at Macmillan Learning have a ton of help articles in our Support Community. What is the best way to find what you're looking for?
If you are just getting started, there are "Getting Started" pages for each of our digital products. To find them, go to the main support page (https://macmillan.force.com/macmillanlearning/s/) and scroll to the bottom to find the digital product that you're using from the list of icons.
If you click on, for example, the logo for Achieve, you will be directed to a page where the articles are organized by Topic and there is a "Getting Started" link at the top.
If you are new to the product, I'd start with the Getting Started information. If you know generally what you're looking for, say something about student refunds, simply click on that "Refunds and Returns" box to find a number of relevant articles. (Keep in mind, those articles will be for both students and instructors.)
I would then recommend that you use the filters (Role and Products, for sure) and then search for the topic such as "extra credit." You can use the Article Features option to search for articles with videos. When you narrow your search using the filters, in this case, Instructor using Achieve, then the article that comes up (see in the gray box) is more likely to be the answer you need.
I've been working in publishing since 1997, doing everything from the front desk to marketing and sales, and a few things in between. And I love working working with media and helping students succeed.