To get to Uranus, you must defeat Kela de Thaym on Merrow, Sedna.
With the Echoes of the Sentient update in September 2015, much of Uranus is marked as Submersible, meaning an Archwing is required. This quest is available at Mastery Rank 2 and tasks you with finding and building an Archwing. The first mission involves traveling to the Void through Venus and recovering a cache. The second mission is an excavation and tasks you with retrieving Wings, Harness, and Systems. These do not have to be done on the same playthrough, and the mission can be attempted multiple times in order to find one missing part. Once the Archwing is built, a final mission starts as an Exterminate, but involves an abrupt switch to Archwing, hiding from a Balor Fomorion. After this, the quest is complete and your new Odonata Archwing is available for use.
Tyl Regor is a melee boss that fights you in three distinct phases, but his fighting style does not really change. He charges Tenno, uses Smoke Screen to hide his position, and teleports erratically to throw you off.
After losing the first third of his health, he floods the bottom section of the arena, turning it into a Submersible section. Following this, he teleports away and unleashes a crowd of Grineer Manics. He comes back after defeating every Manic.
After losing the second third of his health, get to higher ground!
There are catwalks above that you can reach with Bullet Jump (
while pointing where you want to go) and it is imperative to get up here. Regor will then flood the rest of the arena and
electrify the water, taking heavy damage while you're in archwing. Water jets will also come out of the walls, which can push you into the water. Another wave of Manics, this time including Manic Bombards. After defeating all of them, Regor will appear again; kill him and leave.
Between Tyl Regor and the Manics, you will have very few opportunities to stay at range. Rhino, Frost, Valkyr, or Saryn would be good choices for their large health pools and armor. Either melee or short range, high damage per shot weapons are best for this fight.