You need a manometer, but you can make one with a meter stick, some clear plastic pipe, a few cable ties and some coloured fluid (I used blue coolant fluid, don't drink it!)
Otherwise you can use some vacuum gauges, fairly cheap on eBay.
In short, you'll connect your manometer or vacuum gauges to the vacuum nipple on each throttle body and then tweak a specific screw on the throttle bodies to ensure they both suck equally.
The service manual shows how to do this in detail, get it from the
downloads section.
There is also a
Search function on the forum, almost everything you could possibly ask has been asked before