How can I access the RHEV-M REST API?

First, ensure the package is installed:

[root@hostname ~]# rpm -qa | grep -i rest

rhevm-restapi-3.0.0_0001-19.el6.x86_64

(or similar)

It is now only available via HTTPS and via the /api path (rather than /rhevm-api). Assuming you selected defaults in the install then HTTPS will be on port 8443 so your URL would be something like:

https://hostname.rhev.local:8443/api