Make sure you've set up your Math Wallet extension according to the directions in Download & Setup.
You will need to open Web Wallet in order to view account details and perform transactions.
Please select the wallet you want to open and click Web Wallet on the Math Wallet extension popover interface.
After clicking Web Wallet, a new tab will open asking you to login into Math Wallet, click on login and you will enter the Web Wallet.
Specify the shard you want to pull funds from using the Shard dropdown in the sidebar.
Specify which account you want to send funds to using the To Address field.
Specify which shard you want to send funds to using the Shard dropdown to the right.
Specify the amount you wish to send in the Transfer Amount field.
Specify the gas price you wish to pay using the Fee slider. Gas is a fee charged by the network for the computational work of mining a transaction into the blockchain.
Click Transfer to complete the transaction! You will be shown a transaction receipt before finalizing the transaction.
If you would like to use Math Wallet to interact with other Harmony networks such as Testnet, you will need to switch networks.
In the toolbar at the top of the page, there is a drop down menu which defaults to Harmony where you can specify which network you wish to operate on.