How to create sub category?

I am trying to set up a sub category in zen cart,
Example being like i have drink as my category and i would also like to have tea and juice as two sub categories under the drink category.
Thanks,

Admin>Catalog>Categories/Products
Go to Drink category and then you'll have a button "New category"
You cannot have both subcategories and poducts under the same category.

i was looking at your website http://andila.co.uk and how can i achieve the effects of your category-
bikes-bicycle accessories-related products?
and the scale of your website is really good, would you please give me some advice on how to deal with the size and scale of the website

You can use a full width template. I used the zencart_zen template, available in the free add-on section. You need to keep in mind that the template will stretch with the size of the user's monitor/resolution, so you'll need to test it to make sure it's displaying right.
The category effect is the simple switch in admin:
Admin>Configuration>Layout Settings>Categories - Always Open to Show SubCategories

We have Categories Always Open to Show SubCategories i
just noticed, But still doesnt work?
Not sure if something else is not set up maybe why?
Still need some help,
Thanks,

We need to see your site to answer that.

here is the link
https://www.chrismaddox3d.com

Template Monster is notorious for disabling standard admin functions, so if something that ought to work doesn't, my first thought would be that they have bypassed or overridden it in the template code. You should ask them to fix what they have broken. You also have a problem with the sideboxes duplicating themselves, which I am sure the original TM code does not do, so you might have made some change that disturbs even the TM files. It's impossible to tell what from here.