Enable cloudfront for wordpress and php app

Hello, we are about to launch a new product and need some help here. this is what we want to achieve.

our main site is on www.example.com which is a wordpress multi-site on sub-directory level. and we have a php app thats on app.example.com now we want to use aws cloudfront (custom origin) to serve static files(css, js & image) for both the site & application. also is there any way to set certain file types only? is it possible to have single distribution for both? if yes how can we do that? even if we need multiple distributions that ok but please give us some guidance here. i have read all the articles from aws but there are not that understandable for newbies like me.

i also want to say, we want to make this without any plugin if possible. because plugins not gonna cover our application and we are really trying to avoid any 3rd party plguin here if possible.

thanks in advance.