Have the character rest for a minimum of 1 hour and the Level Up screen will appear. Once your character has increased their Major and/or Minor skill ten points, a message will appear on the screen indicating that your character should rest and what they have learned.
When the number reaches 10/10, the character will increase in level. The X is how many 'points' the character has towards the next level. You can always tell how close a character is to leveling by looking at the bar next Level in the Stats menu. This can be any combination of Major and Minor skills, so long as they have been increased a total of ten times. In order for your Morrowind character to increase in levels, your character must increase in a Major or Minor skill 10 times.
