To get started, you will need a device dump or an file. You can find a collection of these at the Symbian OS ROMs Collection on Internet Archive.
Use tools like Navifirm+ or archived firmware repositories to download files for a supported S60v5 device (e.g., Nokia 5800, RM-356).
Spend some time exploring the new features and settings available on your device. You might discover functionalities you hadn't noticed before.
S60v5 ROM for EKA2L1: The Ultimate Setup Guide for Symbian Emulation
A .zip or .7z archive containing the extracted file system of a device.
is particularly sought after because it brought touch-screen capabilities to Nokia devices.