|Specs show that comes with a DVD writer. Is that not working?|
Here's the bios setup guide for that model:
It doesn't show any USB boot options. A few things to try though:
Enable 'USB legacy support' from the Advanced menu. And I think I've seen sometimes the regular cd/dvd boot option will include an external optical drive.
Also note it has a list of devices 'excluded from boot order'. Examples showing there are USB hard drive and USB memory (flash drive I guess) and you can enable those by tapping 'x' when they're highlighted. Try enabling whatever shows there on yours and maybe it'll then pick up your external cd drive.