At the water connection on the left under my kitchen sink there is a slow drip. There is a twist turn but I don't want to turn it. What should I do?

Is it leaking directly from the valve, behind the handle ?

Is the leak coming from angle valve? See picture below. If coming from packing nut, tighten nut. Use one wrench on nut and another on housing.

Chuck

Just another picture to compliment the above answers regarding tightening of the packing nut... see image... ;)

Use two wrenches as suggested by Chuck.

MARK