How do I record an expenses paid by me for a business expense that I do not get reimbursed?
It a debt Vs shareholders. It depends from your local laws if it can be considered a liability or equity.
Enter an expense claim. See the Guide: https://www.manager.io/guides/6898. Your form of organization will determine whether to set yourself up as an expense claims payer or allow the claim to be posted to your capital account.