Sync Your Preferences

The Advanced tab is where you set the location to which Alfred preferences will be saved. Whilst they recommend a cloud service, and in particular Dropbox (I've no idea why Dropbox would be especially superior), you can choose any cloud service you like (that has a locally accessible shared folder on your computer); or you can just choose an ordinary local folder that isn't stored in the cloud.
I, personally, use my iCloud folder to store the preferences in.
Just have a read of the description I've drawn a pink rectangle around, and make sure you understand what is happening. But it's pretty straight forward.
Importing Preferences
Generally, if your preferences are synced, they won't need to be re-imported. But if you do need to for any reason, just locate the preferences file which looks like this:

and double-click. It will automatically open in Alfred and the new preferences will take immediate effect.