To reach Okaara, you must first complete Green Loontern's quest in The Watchtower to unlock the Moon Base. From here, you can build up several Lantern gates to reach the various planets.
Gold Brick #1
As usual, Green Loontern is by the teleporter to give you a tour. Follow him around and take out any Orange Lanterns that show up. After the tour, you'll receive a Gold Brick.
Gold Brick #2
You'll find the Loontern again in a rock structure. This time he needs help fending off some Orange Lanterns. Help him take out 20, and he'll reward you with a brick.
Gold Brick #3
When you next meet Green Loontern, he'll need help getting his statue back. To start, check the river area nearby for a sense spot. Use a sensory character to reveal an arrow, then follow this to another sense spot. Use your senses to reveal a second arrow, which will point you to a large gold wall. Melt down the rocks that compose it to find the statue on the other side. Return this to the Loontern for a brick.
Gold Brick #4
This time around, Loontern is possessed by an Orange Lantern's ring. Chase him down and land three hits to knock the ring away. He'll give you a brick for your help.
Gold Brick #5
Your old bovine friend can be found on this planet too. Talk to her to learn that she needs help learning to fly. Follow her and take out the enemies along the way until she reaches Mr. Mxyzptlk. This will end your quest and earn you a brick.
Gold Brick #6
Like the other planets, you'll find the remaining bricks by following the beacons in the sky, one of which leads to this flying challenge. Pass through each ring before time runs out, and you'll win a prize brick.
Gold Brick #7
There's also a footrace you can find under a beacon. Like the flying challenge, you'll have to dash through every ring before time runs out. Do it, and you'll win another brick.
Gold Brick #8
There's a second footrace to find - and this one takes you underwater. Use a diving character to swim and jump through all the rings like before, and another Gold Brick will be yours.
Gold Brick #9
Under one of the beacons is a flooded temple entrance. Hop into the water with a diving character and bust up the plants to find a switch. Step on this to open the temple, then head inside and take out the Orange Lanterns that appear. The chest holding the brick will open after the fight.
Gold Brick #10
You'll find a second temple under another beacon. This one is guarded by glass windows, which you can break through with a sonar character. Bust up the debris on the other side to find a dirt patch, then use a digging character to unearth some loose bricks. Build these into a lever and pull it to open the nearby chest, which holds a Gold Brick.
Gold Brick #11
Another beacon, another temple. Search the spiral around this one for some brush you can clear to uncover a handle. Grapple this to open a door below, then pull the lever on the other side of it to open the chest atop the temple. There's a brick inside.
Gold Brick #12
The final Gold Brick is inside - you guessed it - a temple. To reach it, use a big character to bust through the cracked wall blocking the entrance. Inside, blow up the silver chest with a demolition character to reveal a gold chest. Melt this down with a laser character to uncover the last brick.