I followed the steps here and here to add the new properties to the Product entity.
In order to add another new tab, I tried these step and I was glad that it works!
1. Go to Presentation > Nop.Admin > Views > Product > _CreateOrUpdate.cshtml
2. Add these codes in the "product-edit" div in the list.
3. Also add this code in the "product-edit" div.
4. Add this at the end of the class too:
I just copied and pasted from the existing tab information.
5. Create a _CreateOrUpdate.WeatherRecommender.cshtml (Just copy from one of the existing file)
6. Add the admin content to the class file,
@Html.NopLabelFor(model => model.WRPublished):
@Html.EditorFor(model => model.WRPublished)
@Html.ValidationMessageFor(model => model.WRPublished)
7. Remember to go to Administration > Languages > Add new resource for "Admin.Catalog.Products.WeatherRecommender", so the value will be displayed as the tab name.