Firstly, the cpanel version is provided by your hosts, not us, and we know it has some problems so you would be advised to bin it and reinstall using our files. We cannot fully support cpanel installations. Your hosts should but they will probably not help you.
A style can be installed but you only see it if you turn on the override option below the board setting so force it on everyone or you actvely choose it in your user control panel.
For forums, they will only show if you set the correct permissions for people to see them
'In Administration Control Panel (ACP) > FORUMS > Manage forums make a new forum (or edit an existing one).
Forum type: Category
Parent forum: No parent
Set permissions for category.
Then make another forum.
Forum type: Forum
Parent forum: the category you just made.
Set permissions for forum.
To set permissions, either use the option to copy permissions from an existing category or forum that has the desired permissions, or:
Administration Control Panel (ACP) > Permissions > Group forum permissions
Set the registered users to be able to see and post in it:
Registered users > Standard access