Need Help with Web Design On Shopify

Hey Guys,

Pretty familiar with HTML but I'm trying to get this design going but I don't know how to upload the source code to shopify. Also not sure how to link the CSS.

http://masonry.desandro.com/

Maybe that's not even the best solution. I need to have the page look like this http://www.necessaryclothing.com/features.html I'm just not sure if there is something out there that will do a grid like that easily.

Thanks so much I'm pulling my hair out trying to figure this out.

I am not 100% sure because Its been a long time I used shopify

CSS and all other files you got in editor panel.

See all files in editor panel in your shopify.