Question: how to add hkcu registry key?
Answer: Find the key/s you want under HKCU in regedit, export it/them.
Now right click on the HKEY_USERS key and select load hive. ... 
in your exported reg file replace all instances of [HKEY_CURRENT_USER\ with [HKEY_USERS\NAMEHERE\ (or whatever you named your hive) and save the file.
double click the reg file to merge it.