Installing a New Add-on

The exact procedure for installing a new add-on will be directed by the creator of that add-on. However, in general, the procedure will be as follows:

1.Download the add-on and unzip it.
2.Upload the add-ons files into your XenForo installation. This will usually create a new directory within the library/ directory in your XenForo installation. In general, this shouldn't overwrite any existing files.
3.From your control panel, go to the "install add-on" page. The add-on will have provided an XML(3770) file somewhere within it. Upload that file there and submit the form.


Upgrading an Existing Add-on

Upgrading an add-on is similar to installing a new add-on. However, you must use the upgrade option for the add-on you are upgrading. You cannot upgrade an add-on 
from the "install add-on" page.

1.Download the new version of the add-on and unzip it.
2.Upload the add-ons files into your XenForo installation. This will overwrite some files.
3.From your control panel, go to "list add-ons". Find the add-on you are upgrading, expand the "controls" menu and select "upgrade". Upload the XML(3770)file that is provided with the add-on and submit the form.

Disabling an Add-on

Disabling an add-on will effectively turn it off. Any integration into XenForo will be removed until the add-on is enabled again. If you have any problems, support
will recommend that you disable your add-ons.

#To disable an add-on, choose "disable" from the "controls" menu in the add-on list. To enable an add-on, choose "enable" from the same menu.


Uninstalling an Add-on

Uninstalling an add-on will remove it from your XenForo installation completely. Any data associated with the add-on is likely to be removed. You will not be able to
recover that data after uninstalling the add-on!

#To uninstall an add-on, choose "uninstall" from the "controls" menu in the add-on list. This does not remove any of the add-ons files that you uploaded when installing it.


Installing a new Style

Refer to this guide : https://xenforo.com/help/styles/