See the 6.2.3 Patch Notes.

Returning in patch 6.2.3 (now on the PTR) are valor upgrades. The following gear can be upgraded twice, by 5 item levels each upgrade, for 250 valor points: all HFC, Kazzak, crafted and Baleful gear but not Highmaul, BRF nor PvP gear. The Ethereal trader in SW or Stormshield can perform the upgrades.

You can earn valor points from completing a random heroic dungeon (100 VP per day), Mythic dungeons (300 VP each, per week), an HFC LFR wing (150 VP each, per week), BRF and Highmaul LFR wings (75 VP each, per week) and some weekly bonus event quests (500 VP). Do them all and you can earn a maximum of 4875 valor per week. See Details.

Currently on the PTR, you can accumulate a maximum of 5000 VP.

To prepare for this patch, try to find a replacement for any Highmaul or BRF gear that you are currently wearing.

Patch 6.2.3 is scheduled to go live on November 17th