How do you get threw the gate at the beginning of Toad Town Level?

If you just got that portal with the Bros.Ball then don't worry about it right now. Go outside to the third floor and there should be a new portal.
Acgmindmaster12

At the top right of the village, you'll see a house with a bridge coming out of it. Use the baby drill and enter the gate at he bottom of the house. Climb up and go across the bridge into the next part. Climb down and go down through gate. You'll seetwo coloured floating blocks, one translucent and one opaque. Go under them and change back to Mario and Luigi, take them to the floating blocks also and hit each one inorder, starting with the opaque one. You''l open the gats, but you'll still be split up till you get to he next checkpoint. Hope this helps!

Just telling you, its not the beginning, its the end. Secondly, you must wait until after the Koopaseum, Underground Cave, Thwomp Volcano, Inside of the Thwomp Volcano, Eruption of the Volcano, and Shroob Mothership. You'll be in Toad Town after all of this, then, you'll adventure as seperate brothers. Near the end is the Star Hill warp pipe, and you'll have to get to the Star Shrine there. But, you didn't think about going to the right place first. When you get to the other side of the gate, make sure you hit the switch to open the gate permanently. go to the desert first before trying to get on the other side of the gate.