how to make differrent sizes of one multicolumn

[Anum990]

I want to create different sizes of one multicolumn in e.g one size for desktop and other for mobile screen 

for reference i suggest please check out "Lulusar.com" 

I want my multicolumn just like that.

[Anum990]

tell me how and where i have to paste this code

[Anum990]

please tell me exect location where i can paste HTML code I want to edit multicolumn.liquid