A nylon string guitar is fitted with three unwound strings (strings 1-3) and three wound strings (4-6). It is important to have the correct set of strings fitted to your guitar, especially if you are a beginner.
There are basically three types of strings available for the nylon string guitar, high, normal and low tension strings. Until you build enough strength in your hands to fret the chords cleanly, low tension nylon strings are recommended. A reputable music store which sells guitar strings should be able to assist with this. Do not put steel strings on a nylon string guitar or it will damage the neck of the guitar.
Strings must be correctly fitted to the guitar otherwise you will encounter tuning problems. In the early stages of learning the guitar it is recommended that you get a qualified guitar repairer or an experienced guitar player to fit the strings to your guitar.
Tying the string to the bridge: There are basically two methods to tying the string to the bridge of a nylon string guitar. Study the following diagrams. With both types of knot shown it is important to finish the knot behind the back of the bridge. This will reduce the possibility of the string slipping.
Tying the string to the tuning key: It is important to have a short length of the string protruding through the hole in the tuning key barrel. This part of the string can then be clamped to the barrel as the string is coiled onto the barrel. See the adjacent diagram. The string should coil neatly around the barrel at least 4 - 5 times.