Android Custom ROM Missing “Add Google Account” Option
That's pretty normal for (almost) all Custom ROMs: They are not permitted to include Google Apps. GApps are proprietary, and to ship them bundled with anything requires an explicit license from Google.

However, Custom ROMs come rooted usually. and also usually, you (at least in most cases) have a custom recovery when installing them. So if you feel you need a way, you've got two choices primarily:


pick the GApps package corresponding to your Android version from Goo.im, and flash them via your custom recovery, or
head over to XDA and check for the NOGAPPS packages if you prefer an open-source replacement