Rey, do you have access to your root folder of the tiki installation? If you really want to add the lock file manually you can simply go to:
public_html/db/ and add create a file named "lock" without an extension.
or your installation may be in a subfolder public_html/root folder/db/
When creating the file do not add an extension to it, such as .php or .sql or .ini or any extension for that matter. See attached image.
If you do not have access to your root folder for the tiki installation it really is an easy thing to do as Rick suggested run the installer again by www.yourdomain.com/tiki-install.php and skip to the last step to activate the installer lock.
See image below for lock file.