Hey K-B,
Have you had a look through the Documentation on the SuiteCRM docs site?:
It should contain all the required setup and pre-requisites
There is also a Thread: https://community.suitecrm.com/t/api-setup-and-example/
Where users have discussed minor issues/resolutions on setting up the API
Hopefully a combination of the above can point in the right direction!
Let us know if you have any issues 