You can link to Visual Fractions or cite the website as a source using the below.
Link to Visual Fractions
Copy and paste:
<a href="https://visualfractions.com">Visual Fractions</a> - Learn fractions with visual models. January 1, 2020.
Cite Visual Fractions
Copy and paste:
Visual Fractions: Learn fractions with visual models. January 1, 2020.
Please note: you must use the date and year you read the source here. And, of course, make sure to use the correct link and title you are citing.