It depends on how do you perform installation.
There are ready to go packages described [here](https://gluu.org/docs/oxd/install/)
Or otherwise you can perform manual installation described [here](https://gluu.org/docs/oxd/install/#manual-installation)
Since you tried to build it I guess you would prefer manual installation.
Not sure which branch you did try to install, our latest official version is `3.0.2`, [git branch](https://github.com/GluuFederation/oxd/tree/version_3.0.2).
Latest not officially released yet `3.1.1` located [here](https://github.com/GluuFederation/oxd/tree/version_3.1.1)
However there is no need to build them by hand, you can find respective zip's in maven repo:
- https://ox.gluu.org/maven/org/xdi/oxd-server/3.0.2/oxd-server-3.0.2-distribution.zip
- https://ox.gluu.org/maven/org/xdi/oxd-server/3.1.1-SNAPSHOT/oxd-server-3.1.1-SNAPSHOT-distribution.zip
About configuration, there is no need to create any file manually. Once you unpack zip file (or install linux package) you should be able to find confgiration under 'conf' directory.
- conf/oxd-conf.json
- conf/oxd-default-site-config.json
Documentation describes what each configuration property means.
I hope it helps.
Thanks,
Yuriy Z