You can find Mosspaper's Widget here: https://app.mosspaper.com/d/#/widget. There are 2 sizes available for you to embed into your web site.
1) Log Into your Wix web site.
2) Click on the page you would like the widget to be placed.
3) Click on "Add".
4) Scroll down to " "Apps".
5) Under Apps, Click on "html".
6) You will see a html setting box.
7) Switch the mode from "website address" to "html code".
8) Copy and paste the iframe code into the designated html code field.
Paste it and click "update".
Check out the widget here: http://mosspaper.wix.com/test