When I do a WEN oil treatment, I do it on dry hair. I'll draw up a dropper full of oil and run the point of the dropper along my scalp, in all different directions, releasing the oil as I go around. I'll do that probably 3 times, maybe 4. Then I'll comb it all through before doing a very loose twist to my hair and piling it on my head. I'll wrap my head in a microfiber turban towel, making sure none of the hair moves and accidentally gets in the part that gets twisted. If I do this at night, I'll go to bed with the turbie towel on (yeah, my hubby loves that look, not to mention the smell...lol). If I am doing the treatment during the day, I'll leave the towel on for several hours. When I'm ready to wash it all out, I use a little WEN Cucumber CC for my first cleanse because my gut tells me I need something a little more clarifying to cut through the extra oil. I'll follow up with a second cleanse of any random mixture I choose. If you are using a shampoo, I'd probably use your normal kind, but add just a little bit of clarifying one with it. You don't want to have a harsh, clarifying shampoo to strip out all the good you've tried to accomplish with the oil treatment.
In the days following your treatment, you can probably add a few drops of coconut oil to your shampoo, too, to keep the benefits going long term. My daughter does that with WEN Tea Tree oil and her WEN CC. Don't overdo it - just a few drops in the palm of your hand and mix with your shampoo.