Need guidance on Implementation of PM/ITSM tool as fresher PM

Hi All,

I have recently joined a startup as IT PM, we are working with another mid size company who want to implement project management system(till now they had nothing just basic email/excel workflow), demo was on the day I joined. I was included in that call as well. Now expectations are that I am going to lead the testing phase of this PMS. 2 technical resources will get aligned and we have get it done within 15 days so it can go live by August 1st. It also include ITSM which want to have in future, currently they don't have anything as IT operations. basically they want to replace current manual method of receiving requests, assigning delivery resource, executing, tracking, monitoring, handover & closing actions / projects as well as individual deliveries (i.e small service requests).

I had a basic discussion with IT delivery lead ,whose team will use this,to create detailed project plan and scenarios. there is no Service desk coordinator as of now, I will be playing that role till the time they hire someone. I do have some scenarios in mind like which can be tested like Roles who can do what and request flows, am I in right direction?

I am confused about What should be discussed, how to make a plan, what to include.

I am new to Project management, I was working as IT recruiter earlier I have good understanding of ITSM but not much of official documents and cybersecurity as domain I have basic understanding. joined just few days back.

sorry for long post.