this is for Text Adventure version of quest, but it shows well how to do it:
http://docs.textadventures.co.uk/quest/guides/character_creation.html
and here's how to do it in GameBook version of quest:
'Pages' -> 'Page1' -> Page type: [script+text] or [script]
'Pages' -> 'Page1' -> Script: -> (see below)
add new script -> output -> 'print a message' Script -> print [message] Name?
add new script -> output -> 'get input' Script
-> then -> add new script -> variables -> 'set a variable or attribute' Script -> set variable player.alias = [expression] result
add new script -> output -> 'print a message' Script -> print [expression] "Your name is " + player.alias + "."
// I type in: HK
// outputs: Your name is HK.