how to show Category and Sub-Categories always?

hello every one.
is there any way to show Categories and Sub-Categories exactly the same as picture below while i enter my site ?
and after i choose one category ,it`s normal.i just want to show sub-categories under one of my main category,because there are so many good itmes under these sub categories.
thank you so much.

You could set your site to Always Open to Category and that Category ...

Configuration ... Layout Settings ...

Categories - Always Show on Main Page
Always Show Categories on Main Page
0= off
1= on
Default category can be set to Top Level or a Specific Top Level

Main Page - Opens with Category
0= Top Level Categories
Or enter the Category ID#
Note: Sub Categories can also be used Example: 3_10

Now your Home page will start like usual, but have that Category open with the subdirectories showing when another category is not selected ...

thank you so much.
the question is that how can we still show the same main page as before? just the side box about category changed.

Switch to the Classic Template ... does it look normal except now has that Cat box open with subcats showing?