A higher front sight is needed. As mentioned, a popular and easy way to accomplish this is to strip a bit of insulation off of some appropriate-sized wire and slip it on to the front sight, then trim it to length. It works, and makes no permanent change to the rifle.
A more permanent fix is to replace the front sight, which is usually not too hard a job. Drive out the pin that retains the front sight hood and tap the hood off of the barrel. You will seee that the front sight is shaped like a small nail, fitting up through a hole and being held in place by the "head" of the nail. It may slip out of the hole easily, or it may take a bit of struggle to get it out, but come out it will. I replaced mine with -- what else? -- another small nail, this one brass. Reinstall everything and take it to the range, along with a small file. It's then a simple matter of shoot-n-file until you've got it right.
Personal preference, but I like the brass nail I used -- a bit thinner, making it more precise, and a bit easier to see. But a steel nail will duplicate the look of the original.