If you drop the anchor over the side in the middle of the boat you will eventually go swimming in a current or wind or boat wake. If you anchor off the bow or stern you will go swimming as you try to crawl to the bow to grab the anchor rope. So you need someway to move the anchor rope from the middle of the boat where you can grab it to the bow of the boat where you can use it. A trolley will do. With my canoe I run the rope through a toggle at the bow and bring the end of the rope back to where I sit. This allows you to raise and lower the anchor but not pull it back into the boat completely. I have seen people use the same rig with a second short rope connected to the anchor rope with a loop that will allow them to pull the anchor back to the middle of the boat. While there different ways to accomplish it you need to have the anchor at the end of the boat controlled by you in the middle of the boat.
Canoe / Kayak Anchors
Recreational Kayak Paddle