Change amount of posts listed

I run my https://www.backpacker.it with ad-clerum-10 Template.
I would like to know if it’s possibile to show a selected amount of posts in the main page and a different amount of posts in the categories.
For example right now there are listed 5 posts in the main page and also five posts when you search in the different categories in the left sidebar (CATEGORIE).
I wonder if it’s possibiel to stabilize a different amount of posts listed inside the varios categories. I would like 5 posts listed in the main page and 10 when you search inside CATEGORIE.
Can you help me if it’s possible and how?
Thanks!
Stefano