Most small Ltd companies need a Director's loan account in the books to record not only sums lent to and repaid from the company's bank account but also to record expenses paid personally by the director or salaries and dividends recorded but, as yet, unpaid.
CB makes this very easy by having a dedicated bank account to act as a director's loan account, ie in much the same way as you'd create a bank loan account.
So, unless you have already done this, head for the Bank screen and hit Add account, then hit "Add" next to "Directors loan account" and fill in the details.
From then on you can use it as you would any other bank account and so, in this case, when you come to explain the £500 coming into the bank account use the "Transfer" tab and select the Director's loan account. When you then look at the Bank screen you'll see your director's loan account in overdraft by -£500, indicating the company now owes you that money.