Hi,
In the backend, you can access to "Display > Custom fields".
By creating a "New" custom field, you will be able to choose the table (witch is the type/target) and you have to choose "item".
After that you can create the type you want, a textbox, a dropdown, etc.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.