You don't connect to TamaTown. You go on and get items through games or buying them from stores, you have to go to the password option on your V3 which is on the icon for games and scroll down to find it. The passwords are made of numbers, just enter the code into your toy and you will get the item.
Getting items from stores requires Gotchi points and items from games are givien free.
accually,when it asks you for your username you have to type int he user you have for your tamagotchi,your tama is connected to tamatown because of the antenna thing,that's why you can'y use passwords other ppl give you!HOPE IT HELPED!
The V3 doesn't actually connect to tamatown, the antenna is just for show.
And to take trips you have to buy a ticket on your tamagotchi in the shop (they show up sometimes) then after your tamagotchi returns it will give you a password. You enter this password on tamatown in the travel place and you get a password for your tama, which will give you a souvenir.
Also it is very important to enter the correct user name, the one on your V3, otherwise the codes will not work.