How can we apply 5S system at supply chain department in purchase process and documentation purposes?

Any Purchasing Department following basic guidelines as mentioned here under would automatically achieve 5S.

Any Purchasing Department must have following guiding principles before it while making procurement decisions:

• PROPERLY AUTHORIZED PROCUREMENT
• WELL DEFINED AND NON-DISCRIMINATORY EVALUATION CRITERIA
• OBTAIN VALUE FOR MONEY
• Transparency
• Open and fair competition
• Proper Documentation
• Probity
• Accountability
• Ethical Behavior
• Compliance to SEE- Social Economic and Environmental considerations

I really don't get the question. It's pretty clear: Sort, Set, Shine, Standardize and Sustain.