The staking dashboard requires you to sign transactions with Metamask. If you do not know how to setup Metamask, you can visit our Injective Learn resource: How to Setup Metamask.
Open the staking dashboard: https://staking-testnet.injective.network/
Click on the Metamask option and complete the signature request by clicking Sign. This will allow you to access the dashboard dapp, where you will be able to view validators and delegate your INJ tokens to validators.
From the top menu bar, click on Wallet to open the wallet page.
Under My Balances you should be able to see how many INJ tokens you have in your wallet on three networks: Mainnet (Ethereum Network), Kovan (Ethereum Testnet), and on Injective Chain (Equinox Injective Testnet). The amount under Mainnet should reflect the amount of ERC-20 INJ tokens you have available in your wallet.