In KMyMoney, a loan is a type of account. Therefore, to create a new loan, you begin by selecting the → menu item. Continue by answering the questions that the wizard poses to you.
Optionally, a loan can be associated with a particular institution. If you are borrowing from a mortgage company or a car loan company, you could create an institution entry that describes this firm and associate the institution with your loan. If you are borrowing from your Uncle Ted, there is no requirement to set up an institution.