I need reseller or partner certificate from OEM

I'm filling the Government Tender and its required the Authorized letter from company. Now I am supplying laptops to schools and government officials. But I want to sell items through the Government eMarketplace (GeM) portal. I have a GeM ID also. But I need reseller or partner certificate from OEM so that I can add product on GeM portal. I filled Tender as Firm. Need help if any one is here to guide me.

Thanks