add some instructions for using tx requests

point-of-sale/README.md

@@ -74,8 +74,8 @@ open "https://localhost:3001?recipient=Your+Merchant+Address&label=Your+Store+Na
 You may need to accept a locally signed SSL certificate to open the page.
 
 ## Accepting USDC on Mainnet
-Import the Mainnet endpoint, along with USDC's mint address and icon in the `client/components/pages/App.tsx` file.
-```jsx
+Import the Mainnet endpoint, along with USDC's mint address and icon in the [`client/components/pages/App.tsx`](https://github.com/solana-labs/solana-pay/blob/master/point-of-sale/src/client/components/pages/App.tsx) file.
+```tsx
 import { MAINNET_ENDPOINT, MAINNET_USDC_MINT } from '../../utils/constants';
 import { USDCIcon } from '../images/USDCIcon';
 ```
@@ -94,7 +94,7 @@ minDecimals={2}
 
 When you're done, it should look like this:
 
-```jsx
+```tsx
 <ConnectionProvider endpoint={MAINNET_ENDPOINT}>
     <WalletProvider wallets={wallets} autoConnect={connectWallet}>
         <WalletModalProvider>
@@ -117,7 +117,23 @@ When you're done, it should look like this:
 
 [Transaction Requests](../SPEC.md#specification-transaction-request) are a new feature in Solana Pay.
 
-**More details coming soon!** <!-- TODO -->
+In the [`client/components/pages/App.tsx`](https://github.com/solana-labs/solana-pay/blob/master/point-of-sale/src/client/components/pages/App.tsx) file, toggle these lines:
+
+```tsx
+    // Toggle comments on these lines to use transaction requests instead of transfer requests.
+    const link = undefined;
+    // const link = useMemo(() => new URL(`${baseURL}/api/`), [baseURL]);
+```
+
+When you're done, it should look like this:
+
+```tsx
+    // Toggle comments on these lines to use transaction requests instead of transfer requests.
+    // const link = undefined;
+    const link = useMemo(() => new URL(`${baseURL}/api/`), [baseURL]);
+```
+
+The generated QR codes in the app should now use transaction requests. To see what's going on and customize it, check out the [`server/api/index.ts`](https://github.com/solana-labs/solana-pay/blob/master/point-of-sale/src/server/api/index.ts) file.
 
 ## Deploying to Vercel