Filled the models and the admin files of the project accordingly.

stefan_gomez_reading/bookshelf/admin.py

+from django.contrib import admin
+
+from.models import Author, Books
+
+class AuthortAdmin(admin.ModelAdmin):
+    model = Author
+
+
+class BooksAdmin(admin.ModelAdmin):
+    model = Books
+
+
+admin.site.register(Author, AuthorAdmin)
+admin.site.register(Books, BooksAdmin)

stefan_gomez_reading/bookshelf/apps.py

+from django.apps import AppConfig
+
+
+class BookshelfConfig(AppConfig):
+    default_auto_field = 'django.db.models.BigAutoField'
+    name = 'bookshelf'

stefan_gomez_reading/bookshelf/models.py

+from django.db import models
+
+
+class Author(models.Model):
+    first_name = models.CharField(max_length=100)
+    last_name = models.CharField(max_length=100)
+    age = models.IntegerField()
+    nationality = models.CharField(max_length=20)
+    bio = models.TextField(max_length=700)
+
+    def __str__(self):
+        return '{}, {}'.format(self.last_name, self.first_name)
+
+class Books(models.Model):
+    title = models.CharField(max_length=100)
+    author = models.ForeignKey(
+        Author, 
+        on_delete=models.CASCADE
+    )
+    publisher = models.CharField(max_length=100)
+    year_published = models.IntegerField()
+    ISBN = models.IntegerField()
+    blurb = models.TextField(max_length =200)
+
+    def __str__(self):
+        return '{}'.format(self.title)
\ No newline at end of file

stefan_gomez_reading/bookshelf/tests.py

+from django.test import TestCase
+
+# Create your tests here.

stefan_gomez_reading/bookshelf/views.py

+from django.shortcuts import render
+
+# Create your views here.