You can update your business details within SimpleClinic at any time. This is done from Business Setup -> Your Clinic -> ensure to click Save after all changes.
The recommendation for logos is to be jpg and within the following sizes:
- square is 300px
- rectangle is 450px.
After updating your logo, you will need to clear your cache to see the updated image as your browser will have cached the old image so it doesn't have to download it every time the page loads: How to clear cache
If your logo does not update, you will need to reduce the size and try again.