When you first set up your Koala Wallet no addresses are automatically created for you. The main page will show your assets' balances after adding them. Do do that, atop your list of assets, press the "+" button.
You will see a list of all supported blockchains and assets. As support for more and more blockchains are added, the list may grow. Tap the "v" button to expand it and show all supported blockchains.
Tapping the blockchain name at the top will filter the assets to only show the ones belonging to that blockchain.
Simply press the + button beside the new asset you want to make visible. If that asset is already added to your main screen, a second one will be created. Repeated assets are grouped together on the main screen. Tap the group to expand it and show all duplicates.
By swiping an asset to the right on Koala Wallet's main screen you have the option to hide or rename it.
You can hide wallets of assets you don't use by tapping the "trashcan" icon. Hiding a blockchain's main wallet will also hide all of its tokens (for example hiding Ethereum will hide all of its tokens). Don't worry, hiding a wallet doesn't move funds anywhere and doesn't prevent it from further receiving funds. When you re-add it, balances and transactions will be fully loaded, even the ones received while hidden.
To better organize your funds, tap the "pencil" icon to rename it. This is helpful if you have multiple wallets of the same asset, for example "Ethereum #1 staking", "Ethereum #2 games", "Ethereum #3 savings".