Doodling is great way start your work.
Using software tools like ERDPlus, you can draw your ER diagram. It can then help you to turn your ER diagram into schema and SQL commands.
You can import this sample file to try out.
Create your database on your SQL server. Tools like ERDPlus can generate the SQL code for creating the tables and relationships for you.
https://drive.google.com/drive/folders/14gV2bM_Z_a7dyazC0Rzv-KSrwpdfxL2R
To test or to run your system, you need real, sample or even dummy information. You have to collect these information and format them for your application.
Export your information from a Google Slide and upload to you database is usually more efficient.
https://drive.google.com/drive/folders/14gV2bM_Z_a7dyazC0Rzv-KSrwpdfxL2R