How do you ensure to excel at your workplace, when you are the only rep for the sales process and you are new to the market, product, and process?

In my view, excelling in the workplace starts with knowing what your superpower is, positioning yourself to spend as much time as you can doing that thing, and telling your direct reports what that you intend to excel.

More specifically for selling in a new market - it’s about planting seeds and laying groundwork. Maybe try explaining to new prospects what your understanding is of the market and product, but that you’re interested in a customer-centric holistic view and what they think. 

Be engaged and document everything - successes, failures, and works in progress. Bring that info to your direct report for consultation on ways to excel in the future. You got it.

Oh this is my jam! 

I'd first get with the founders, other SMEs and any clients (or worst case prospects) you can get your hands on and learn. Understand, not only, what the offering does, but what problems do they solve and who do they solve them for?

If you are lucky enough to currently have clients - find out, tangibly, how you're helping them. Document it, turn it into a case study if you can, but worst case be able to tell the story.

Then use that as fuel for the process and document everything. 
What's working.
What's not.
When does the process stall.
Where are you losing deals.
Everything. 

Those are going to be the challenges you need to solve to continue to grow the business. Get with those aforementioned folks (or other sales folks outside the org) and understand how you can solve those internal problems. 

The coles notes but it's a start