As you kill monsters, win wars and kill other players you will gain experience. The experience that you gain can be spent in raising your stats and abilities. To "spend" your exp, you must enter the exp editor. To do so, type "exp". Type "exit" to exit it. If you have enough experience you will automatically advance in levels once you exit the editor.
Further help is available inside of the editor itself.
You can do commands normally allowed only within the exp editor by using the format: exp 'command'. Thus you can raise skills or stats outside of the editor substituting the command you wish to use as an argument to the exp command. An example of this is:
exp cost combat by 5 exp raise str by 2
1. You will not gain any experience for killing a monster more than 6 levels below your own level.
2. You can not assign your experience points during a war, if you want to have them spent, spend them beforehand, i.e. before the mud shuts down and reboots for war.