For starters, Download A3sync from armaholic at this link

When installing it will ask you to point it at your Arma 3 executable. You can use either "arma3.exe" or "arma3_x64.exe" depending on if you are running 64 bit windows or not. once it's installed you now need to connect it to the repository by doing the following.

1.) Click the "Repositories" tab on the right

2.) Click the blue plus " + " sign on the right to add a new repository.

3.) Under "Public Auto-config URL" paste this link: http://coalitiongroup.net/repo/.a3s/autoconfig

Click "Import" This should auto-fill the rest of the fields to match the image below. Click "Ok"

4.) Select the repository, then click the highlighted button on the right to connect to the repository.

5.) Check "Select all"

6.) Then Click "Start"

Your mods are now downloading!

Setting a different file path

In the case that you want to use multiple A3sync repositories without them deleting each other, you can set each to its own directory

1.) Click the "Addon Options" Tab

2.) Click the blue plus " + " sign on the right to add a new location

3.) Select your desired location

4.) On the Coalition repository page, select your new location as the default destination folder.