For instructions on creating Moonriver EVM and Substrate accounts with SubWallet, please visit Create an Account
If you want to import your accounts from MetaMask into SubWallet, go to Import an Account using private key from MetaMask
Step 1: Log into Moonriver DApp. Select SubWallet, then select the EVM account(s) you want to connect and hit Connect.
Step 2: After logging in, the DApp will automatically prompt you to connect your Substrate account. Select the account(s) you want to connect and hit Connect.