Thanks for your posting and using Aspose.Cells for .NET.
If you want to open a file from resource, then you will need to open file using stream. Place your source file into resource stream and then open the file using stream.
Please see the following document how to open file using stream.
Thanks for your posting and using Aspose.Cells.
Please check the following article. It explains how to embed and access resources by using Visual C#. You can also search on the google to find similar articles.