We have several tools available to build reports for Reporting Services. There are two major tools available:
Report Builder
SQL Server Data Tools
Report Builder is a native application available with Reporting Services, which you can have on the server where Reporting Services is running or locally on your developer workstation. With the latest version of SQL Server Reporting Services, the web portal offers you a download link that takes you to the Microsoft download site, where you can find the installation media for Report Builder:
Getting started with installation of Report Builder
With SQL Server 2017, Reporting Services is no longer a part of the installation media and has to be downloaded separately. You'll see a link in the installation wizard, which will open up a website, where you can then download the installation file for Reporting Services:
Link to download Report Services
You can find the installation media at https://www.microsoft.com/en-us/download/details.aspx?id=55252, where you can download a small installation file (around 100 MB). This file is used to deploy Reporting Services either to a standalone server or the same server running other SQL Server Services.
For the installation itself, you'll need a proper product key; otherwise, you'll be able to install one of the free versions only for evaluation. As the installation is separate from the SQL Server itself, the configuration of Reporting Services will require a running SQL Server, where Reporting Services will create a database: