There are proper steps defined in the qlikview release notes.
Please find the document attached to the link mentioned below.
Go through page no 22.
Hope that helps
Also make sure to backup folder C:\ProgramData\QlikTech before you do the migration to version 10. There has been a change in the folder structure between version 9 and 10. So if you, for some reason, would like to downgrade to version 9 this is not possible if not having a backup of this folder from version 9.