"How you paid" is the account the money came from: your cash, GCash, a bank card, and so on. These are the accounts you set up in the Wallet tab.
On Add expense, tap the account chip (it shows the current account's name, e.g. "Cash") and pick another. That account's balance goes down by the amount.
Want another option, like Maya? Add it as an account in the Wallet tab (see How do I add a wallet, card or account?). It then appears in the list.
Shared expenses don't need an account.