Um. In the Beta Testing forum, right under NEW TOPIC, as shown here:
Before the current Beta expires, a new Beta will show up there. Usually a day or three before.
FYI, that’s at this link: Latest Beta Release, and there are FOUR pieces of software listed (two in 64-bit, both normal and HiDPI; and two in 32-bit, both normal and HiDPI). The HiDPI versions are found a ways down, above the images and below the bugfix list.
And, also, L&L has yet to miss one of these. Sometimes it’s been hours to deadline (I think that happened twice?) when a new one was released, but they’ve not missed one yet.