In order to connect your wallet you have to click on the "Connect Wallet" button on the top-right corner of the page.
There are two options to connect your wallet. One is via MetaMask and the other one is via WalletConnect. You can choose the method that you prefer.
You're most likely not connected to Binance Smart Chain within your wallet.
On Trust Wallet : You can download the TrustWallet mobile application on your App Store or Play Store.After installation, open it. When you go into the dAPP in the top-right corner you can see the different blockchains available, click on it then choose Binance Smart Chain Mainnet.
On MetaMask: It is a browser extension that interacts with the DAPP using the web3 technology.
Create a custom RPC with the following:
Network Name: BSC Mainnet
New RPC URL: https://bsc-dataseed.binance.org/
Block Explorer URL: https://bscscan.com/