2004 Chevy Tahoe Serpentine Belt Installation

I have removed my upper serpentine belt, when I removed the alternator. I can't get the belt back on. They doesn't seem to be a pulley tensioner. Where there is usually a tensioner, there is only a fixed pulley. The belt goes around this pulley, the alternator, the water pump, the crank, the fan, and the power steering pump. They all seem fixed to the block. Nothing to loosen to get slack, and no tensioner to pull back to get slack. I've done this many times on other cars, but am missing something help. Please help.