The essential ingredients:
Modloader64: https://github.com/hylian-modding/ModLoader64-GUI/releases
OoT Online: https://github.com/hylian-modding/Z64Online/releases
OoT v1.0 ROM (you gotta find that one)

Lobby: ScootieStream669
Pass: randomizerchaos669

When you join, the modloader will download the required assets and randomizer settings hands-free!

Upon starting the emulator, it'll show the OoT title screen with Metroid music, at the to of the window you'll see "Mods". You need to enable a setting:
Mods>OotO>Event Settings>Enable 3D Market/Morshu Check this.
Also make sure your controller inputs are working, we can probably help you out if you run into trouble. Once you've got your controls working and enabled the 3D Market/Morhsu setting, quit out of your emulator and rejoin to apply that setting.