Version specific installation and update instructions are given by the Installation Notes section of the Release Notes for each version as found on the Download page. The FAQ also has installation instructions for the current release. This page gives an overview with links to the current release version. To install an earlier release, refer to the Release Notes for that version.
Note for Default Browser and Multi-user Profile
During the "Choose Components" section of the installation, there is a "Set K-Meleon as your default browser" option, but you can set K-Meleon your default browser after installation proccess in Edit -> Advanced Preferences (F2) -> Browsing section -> in General tab there is a button named Set As Default Browser or executing setdefault.exe file in K-Meleon folder.
Also during the "Choose Components" section of the installation, there is a "Multi-user Profiles" option. Uncheck this option to store your K-Meleon user profiles im the K-Meleon folder instead of the Windows user profile folder. When you uncheck this option a file named profile.ini is generated in your K-Meleon folder. (More info about Profile Location)