Ok, in case anyone doesn't know how to run mods with A3 or A2 even. Here is a short tutorial that will get you up and running in moments.
First of all we need Arma3 Sync, or any other launcher. Get A3 sync from here
To download your mods use play with six, get it from here.
You do not need to register to download mods.
1. Create a Mod folder, it does not need to be one the same drive as your A3 install
2. Fire up play with six, go into the settings and direct the download path to your mod folder. It should auto find your A3 install, although we wont use it to launch A3.
3. Either browse the recommended mods via the Play w 6 browser, search for name, or browse through all the supported mods.
4. Create a collection on the main mod screen, you can see it in the image below. Then for each mod you want to install, click the add to active collection icon to the right of the name (small folder icon with + sign).
5. Once you have all your mods chosen, click install, bottom left. The launch icon changes to install when mods are waiting to be installed.
6. Fire up A3 sync and goto the 3rd tab along, Launcher Options.
The options I have chosen are pretty standard ones. The launcher should find you A3 install, if not just browse to it as standard.
7. Goto the second tab along, addon options, very simply hit the + icon, browse to your mod folder and click ok.
8. The main screen, this is where everything is chosen from. Tab 1 from the left, Addons. Once you go to this screen after choosing your mod folder as above. You should see a list of your mods available to use down the left hand side. If not, then hit refresh. I always have mine as a list as in the image below.
Now, on the right hand side, right click anywhere that is blank, and Add Group. Try to keep them organised, ie sound, vehicle, maps etc. Next step is to drag the @nameofmod folder from the left and drop it onto your group name. Once this is done for all you mods, you can choose to select all by ticking the group, or singular by ticking the mod name.
9. Hit start game and find the server you want via the standard in game browser.
Excuse the typos on the images

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Don't forget you can get mods from Armaholic or even directly from the BIS forums. Just drop them into your mod folder and they will appear in your launcher list..