The basic steps are as follows:
- Identify a gene that will provide resistance to the herbicide.
- Based on the sequence of the resistant gene, make a DNA expression cassette that contains a promoter to turn on the gene, the resistant gene, and a sequence to stop gene transcription.
- Transform the plant in tissue culture to incorporate the resistant gene
- Screen for plants that have successfully incorporated the resistant gene and are tolerant to glyphosate.
A very good detailed description of the process is already available at http://sandwalk.blogspot.com/2007/03/roundup-ready-transgenic-plants.html. Additional details about Roundup Ready soybeans are also available in the USDA petition for deregulation at http://www.aphis.usda.gov/brs/aphisdocs/93_25801p.pdf.
If you have additional questions, I would be happy to answer them.