The Stacks Web Wallet is required to interact with a CityCoin smart contract on the Stacks blockchain.
It is a browser extension available for both Chrome and Firefox, and at this time mobile is not supported - use a desktop or laptop!
In addition, each of the contract functions require sending a transaction to the smart contract, with transaction fees paid in Stacks (STX).
How to Acquire Stacks (STX)
As mentioned above, all transactions with CityCoins require Stacks (STX) as fuel.
To acquire Stacks, please see the market list on CoinMarketCap for supported exchanges.
How to HODL CityCoins
All CityCoins are fungible tokens on the Stacks blockchain, meaning they are stored as part of your Stacks account and viewable on the Explorer.
The Stacks Web Wallet allows you to view your balance, send and receive CityCoins, and interact with smart contracts.
An example screenshot from the Stacks testnet is below: