Put in at Stewart's Landing Dam. There is a parking lot right at the put in overlooking the lake and dam.
If the clamshell (tainter gate) is open you can put on the lake and paddle through it. You will rocket down into some turbulent water with a very large recirculation eddy on the left. Stay with the flow you're in on the right side and move back center as the pool narrows and picks up gradient.
When it is closed you can walk a little down Stewart Landing Rd and take a small unmarked path to the river. It is very soon and hard to miss. If you find a larger marked trail you went too far and need to work your way upstream as you walk to the river. Put in next to the concrete wall as far up as you can go.