Ok, so default functions of Odoo are not enough. You found an app that suits your needs and you want to install it. This tutorial will tell you how.
1. Upload the module to Odoo custom addons folder. If you don't know where is that folder simply checks in the Odoo config file (if you followed my tutorials it will be in /etc/YourOdooServerName-server.cfg) I personally recommend Filezilla for file transfer files if they are on a remote server. Please note that in some cases you will have to change the write permission of Custom modules folders in order to be able to save there any files.
2. Activate Developer Mode. In Odoo 10 and older you can do it from Settings, in Odoo 9 and older you would have to click on the username (top right corner) and then "About" - the "Activate Developer Mode button will be displayed.
3. Now go to Apps tab and click "Update Apps List"
4. Remove the default filter and type the name of the App
5. Click "Install" button and enjoy your new App
There are a couple of different ways to do this, including the installation of the App without login to Odoo. They all will be explained sooner or later on this blog. Feel free to contact me if you need any help. You may also want to visit my Odoo App Store
How to install new apps in Odoo on a remote server
Easy, step-by-step tutorial
Odoo Odoo Technical Tutorial