GearSwap is a simple addon that lets you automatically swap equipment sets when switching between your primary and secondary specs. This addon uses Blizzard's built-in Equipment Manager.
Here's a step by step guide for setting up this addon:
Step 1. Download the addon and extract it to your interface addons folder
Step 2. Restart WoW
Step 3. Make sure your character has dual spec
Step 4. Create an equipment set for each spec using Blizzard's built-in Equipment Manager
Step 5. Open the GearSwap config panel (use /gs or /gearswap to show it), then pick the equipment sets you want to use for each spec
Step 6. All done! Now whenever you change specs your gear should automatically change aswell (aslong as you aren't in combat).