The recommended way to install FAL Quota is by using Composer:
composer require mehrwert/fal-quota
You also can install FAL Quota as extension from TYPO3 Extension Repository (TER). Just download and install the extension within ADMIN TOOLS > Extensions.
The extension adds some fields to the
sys_file_storage database table to store quota configuration per storage. After
the extension has been successfully installed, access to a new backend module
FAL Quota in the FILE section  may
be enabled for Backend Users and Groups via TYPO3 module configuration:
The module provides an overview for all storages currently sorted by UID and their configured quota settings .
The extension does not set any quota on installation. If you do not alter you storage configuration, nothing will change for your editors. You need to change the Configuration for quota limits to enable checks.