After I'm finished grading my Lab1a, I was trying to save my certificate for submission when I cannot find the "Save Image" button as stated on the instructions. Though I tried clicking the "Save Frame As," thinking that I might be able to save it as an image, it only shows about saaving the whole web page/format. Is there any way to solve this issue? Thank you!

Some browsers have that issue. You could use Chrome or just take a screencap instead.