*HELP NEEDED* - Starting a Supply Chain/Procurement Function set to scale

Hi All Some of you might remember me from my time at eSourcing provider, Market Dojo. However I have moved on to join a company called Bam in an ops type role. We make all-natural milk drinks in chocolate and banana (they're delicious!) Bam is a new company (6 months trading) and we've recently secured a deal with Sainsbury's and will be available in stores across the UK in 2 weeks time. We're growing incredibly quickly and although the company currently consists of the 2 co-founders plus myself (that's literally it, we outsource manufacturing!) it's time we start thinking about putting processes in place. So my questions are: How does a company establish and build a supply chain function? How do you manage procurement processes in a small company? We need an EDI provider- does anyone have any advice on this? What supplier onboarding processes do you have in place? We're still quite a small company, set to achieve greatness, but at present, large expensive tools are out of budget! Thanks so much in advance for all your help! Anya