I bet it did take you absolutely ages to make a 4 ply!! Great job!!! Now all newly spun yarn should be 'finished'. That is to say the natural skin oils and dirt from spinning should be washed off of the skein. Ties your skein in 3-4 places with a figure eight tie so that the skein stays manageable in a skein form while you wash it. Then with mild dish washing soap and warm water, a sink or bucket, I soak my skeins for about an 1 hour more or less, then I squeeze (don't wring) the water from the skein.
I then take the skein outside and wuzz it. This gets even more water out of the skein. I then let the skein drip dry.
Either on the clothes line of in the shower. You can also lay the skein on a sweater dryer to drip dry. Of course the more water you get out initially the faster the skein will dry.
After your skein is dry, you can wind it into a ball and start knitting, crocheting do what ever You would like with it. The reason you wash or clean the skein after spinning has several reasons. Besides cleaning, you also allow the twist to even itself out in the yarn. Some people also like to "full" their yarn before it is dried. You can do this by beating the skein against a wall or counter top after washing but before drying. Then helps the yarn felt a tiny bit and makes the yarn stronger by allowing the fibers to cling more tightly to neighboring fibers in the yarn and again more even.
Your yarn sounds terrific and I would be excited to knit with it too.