Hi Willa, it depends on the type of material.
If your couch is leather, then this tutorial will show you how - https://www.youtube.com/watch?v=_rs8dhCdI1w
If it's suede then this tutorial should help - https://www.youtube.com/watch?v=huiLCKxbWk8
And if it's covered with some kind of fabric, then try this one - https://www.youtube.com/watch?v=S3bGbDUfkWk
You would be better off to hire a steam cleaner or a cleaning company. If you add to much water you could end up with a damp smelling couch. If it is just small areas like the arms and spots. You can use a spot stain remover and a white soft cloth.
check this out: https://www.hometalk.com/10439154/how-to-clean-a-microfiber-couch-quick-easy
If it is a microfiber couch, you can rent a carpet cleaner from a grocery store (they usually rent them out) and then use the special nozzles to clean it. My husband does this with our couch once a year and it is like new again!
I use the upholstry tool on my carpet cleaner to do mine and clients. I have also used the Dollar Tree Homestore Carpet Cleaner in red spray bottle for touch ups and a soft carpet brush.
For my microfiber recliner, I use a soft baby brush with alcohol in a saucer to dip the brush in and scrub it clean. Works better than my carpet cleaner.