When replying to show a Music video/concert piece (the one you want to show), mouse click the ICON bar seen above your typing. Go right, way right (currently second to last icon on the right) and left click. Now you've done it. Copy and paste the URL on your source.
Hints herein for YouTube etc. If your link does not work, do a search on the source page (ie Robert Plant Rainbow) on the video page you were on (ie YouTube, etc). You will probably find a different URL which ASUS Forum will accept. The original source URL will be accepted on ASUS Forum.
Corsair 500R Case, H110 Hydro, 1200AX PSU, Asus Maximus Hero VI MB, Intel 4770K CPU, Gigabyte GPU GV-N98TWF3OC-6GD, G-Skill Trident 2400MHz 32GB, Crucial M500 960GB SSD, Seagate 6TB HDD x2, Creative SBZ to Denon AVR-4311ci - Infinity Primus 5.1 w/Klipsch Sub XW-300d, HP ZR30w 30" S-IPS LCD, W10 64bit