Click on "+create starter account" and make a new free subscription.
Configure WoW client (4 min)
Open WoW client for your minion character and setup the following.
Open "Main Menu -> Key Bindings -> Targeting" and bind "Interact With Target" to any suitable key.
This keybind works as right click. It asks character to loot a corpse, to run to NPC or target, etc.
Open "Main Menu -> Interface -> Mouse" and enable Click-to-Move.
If this feature enabled, minion will run to its target (including looting, NPC interaction, etc).
Make follow-macro with text /follow Your-Main-Char-Name
Remember to replace Your-Main-Char-Name with its in-game name. Then bind the macro to any comfortable key.
This macro asks minion to follow you. You should use it before moving.
Make damage-macro with text
Remember to replace Your-Main-Char-Name and Your-Main-Damage-Spell with their real ones. Then bind the macro to any comfortable key.
This macro asks minion to damage your target. Use it if you aggred something.
Additional configuration (optional - you can skip this step for the first time)
Install the "EMA" addon.
It does a lot of useful things: auto accept and complete quests, track quests and items, check following and XP, and much more. This greatly helps to watch and control your team in the game.
The actual version can be installed from Twitch. EMA for Classic should be downloaded there.
Add the line /assist YourMainCharName
to existing damage macros.
This makes sure that the minion always picks the same target.
On all characters (minions and main), make macro /script SetView(4);SetView(4)
Bind the macro to any comfortable key.
When you activate this macro, it defaults characters camera and view. With /follow macro your characters will stay together and have the same eye direction, so with this macro you get almost identical screens.
As a variant, you can add this line to your follow macro from step 1.
Make sure your WoW network settings and internet connection settings are the best.
Despite being run on the same computer, all game clients are communicating via a network. So a good internet connection is important. Also, go to WoW client "Settings -> Network" and try to enable "Optimize speed" and "IPv6". This may faster game response.
Run WoW clients and Wow Switcher (1 min)
Go to switcher's window and add all keybinds you made as hotkeys for a switch. Add other keybind which are common for all characters (like damage, mounting, drinking, etc).