there is a 12mm nut on the steering box that will drain the steering fluid, you have to turn the steering to just the right spot to get it to drain. These usually leak on the high pressure line but, because of the plastic outer casing it drips onto the steering box so check the high pressure line. When you refill, fill up the resevoir and turn the steering fully to each side a few times this will fill up the steering box and get rid of most of the air.
2005 320 CDI
2006.5 VW Jetta TDI
1991 560SEL (179000 Sold)
1972 280SEL 4.5 ('The Lead Sled' 320000 miles when sold.)
1972 220D (225000 when sold)