Designing Lotus Notes Databases is nothing, that you can learn from scratch without having any clue or a good teacher.
You could start with the help and click through starting at "IBM Domino Designer Basic User Guide and Reference > Application Design", but I doubt that you will ever be successful.
As long as you do not understand, what Lotus Notes Databases are all about, you will not be able to create even the most simple application.
To give you at least a starting point: Lotus Notes Databases are simple "unstructured" containers for everything you throw in there. Data is presented as "Notes Document" and can contain Structured Data, Images, Attachments, Tables, whatever...
To create a document the easiest way is to create a "Form" in Lotus Notes Designer, create some fields in that form and then use the "Preview in Notes"- Button to show the Form in Lotus Notes. Using Ctrl + S you can save the document, that you created with the form.
Then you use "Views" to show the "documents" that you created.
Now I explained 2 Design- Elements out of 20 "Base"- Design elements, and you might already got lost...
Take my advice: Let someone teach you, how to do this, there is no other sensible way to learn developing applications in Lotus Notes (now Known as IBM Notes)