Defaulting company code and currency key through user profile

Hi

My user wants to default currency key and company code in his transactions.

Normal process is to go to System --> User Profile --> Parameters and i have to give Parameter IDs and Value which needs to be defaulted.

I tried to go to systems --> user profile --> parameters with user id of my user. SAP gave error YOU ARE NOT AUTHORIZED FOR SU3.

So please let me know how i can default these values (currency and company code) in user 's user id with my login.

Please help.