List your main responsibilities and the manufacturing processes in the suppliers you will be responsible for and collect related books on these topics.
Problem solving (
8D, 5Why, etc...) : You will be responsible for solving quality problems in your suppliers.
Capability calculation and Control Charts (SPC): Learn how to calculate capability and stability, normality. Learn at least X-R and moving range charts properly.
Learn how to audit a process. You will sign a PSW or something likewise after making a process audit (for a new project)
Learn basic principles of the manufacturing processes in your suppliers.
Learn how to manage a meeting in a supplier.
Learn how to keep meeting minutes and action item lists. These will be the records after every visit to the supplier.
Learn how to track supplier related KPI's and how these KPI's are calculated (PPM, delivery rating, etc...)
Learn internal auditing techniques.
Many other things can be said. But these will make a good start-up.
Cheers.