Removing a pop up bathtub plug and unclogging the drain can be done with simple tools that virtually everyone will have. The clog is generally directly under the cap at the drain catcher where the screw fits into that holds the cap in place. Gunk builds up in this area, and once the cap has been removed, you can pull out the clog by hand.
Remove the cap. Start by unscrewing the cap that fits over the pop up plug. You should be able to turn it a few times to take it off and set it aside to do the next step. A pair of pliers will help grip and turn it if it is slippery or stuck.
Use a screwdriver to remove the plug itself. Take the screwdriver, turn the screw that holds the pop up plug tight, until it loosens enough to pull it out and then put that aside with the cap.
Find the clog and remove it. Use the flashlight to look down the bath tub drain to find the clog. There is usually a drain catcher not too far down where you can see the build up of hair and anything else clogging the drain. Use the screwdriver or a needle nose pliers to pull out the gunk. You may need to do this a few times to get it all out. Run hot water through it to see if it is clear.
Replace the plug and the cap. Take the plug and screwdriver and turn the screw until it is tight but not too tight. Put the cap on and turn it until it is secure.