Hi jodipu, welcome to the Forum.
Is this your own personal computer or is it an at work computer. If it is an at work computer, then there is a reason why you don't have admin rights, which is precisely to prevent you from trying to do what you are attempting. If you wish to make changes you will have to contact the company's IT section & ask them to help you, which may or may not be allowed.
If it is your own personal computer then you need to set up your user account so you have admin rights.