So after quite a few hours spent looking for a solution, here’s how I solved it 
- Followed instructions in this video : ‘psql’ is not recognized as an internal or external command
- Followed @davbyron thread and replaced required fields + path : psql -U postgres -d baseball -f C:\Users\alexa\baseball_database.sql. More details in the original post Querying Baseball data off platform project - #40 by neoalexandre