You certainly can use any of your sources of personal finance (including overdrafts and credit cards) to fund a new business. In fact, there is no other way to do it.
All businesses are started by individuals or groups of individuals putting up capital. These people are then the shareholders. They receive shares in direct proportion to the amount of money that each puts in. It is immaterial where that money comes from.
When you prepare your first set of accounts, the amount of money that you put into the business can be shown in two forms: Share capital and/or Director's loan (assuming that you are also a Director and that you are setting up a limited company).
Your accountant will advise you on all of this, and I strongly recommend that you use one! Make sure that you don't pay too much, though, because very few are worth as much as they think.