How Do I use these item? I clicked on it, it disappeared and nothing happend.

Its description says that whenever Kzarka will spawn, you will be able to re-enter again (twice).

When you use it its meant to disappear, usually you can only enter Kzarka fight once each time he appears, but after using that scroll the next time he appears you'll be able to enter twice. So the next time he appears just make sure to challenge him again after you defeat him the first time.