How do I adjust the tension for the drive belt near alternator?

The alternator belt is adjusted by loosening the alternator and using the tensioner adjuster bolt to loosen or tighten the belt as required. You are looking for a bolt that is on the top of the alternator, similar to the last picture. Spray some lube on the alternator mount bolts and the adjuster. Then you should be able to back the adjuster bolt out some. Now go to the alternator mounting bolts and loosen them. Now use a bar or soft hammer to move the alternator itself, loosen the tensioner bolt, move the alternator. Then you can remove the belt. To tighten it back up you reverse that process until a belt tensioner gauge reads the numbers in the green circle, or as most people don't have a gauge you can tighten it until the belt only pushes down about a half inch when you push in the area marked C.