You need a SoundFont host. The best free options:

A typical "Essentials" soundfont aims to cover the standard four sections of a symphony orchestra:

How to load (general steps)

At its core, is a SoundFont file designed to provide a complete, out-of-the-box orchestral template. Unlike monolithic sample libraries that require 50GB of hard drive space and a master’s degree in music theory to navigate, this SoundFont aims for simplicity.

Orchestral Essentials.SF2 can be used in a variety of music production applications, including:

If you are just starting and don't want to spend $500 on a professional library, this is the perfect "starter pack" to learn orchestral arrangement. Final Thoughts