Hello Sarah,
You will add a employee for your name. This will allow you to use the expenses function and will also give you the ability to track your own expenses. It it a bit long winded for a sole trader but to use the expenses function, this will be required.
Alternatively, you can just add the expenses as normal bills since you are a sole trader. This maybe better to prevent errors in data entry. If you do choose to just add the bills in, you will not be able to use the mileage tool which is useful, but again needs an employee created.
Regards,
Vanish