memo field reminder

packages/docs/pages/networks/testnets.mdx

@@ -1,3 +1,5 @@
+import { Callout } from 'nextra-theme-docs'
+
 # Namada Testnets
 
 For more context read:
@@ -6,6 +8,11 @@ For more context read:
 
 ## Shielded expedition
 
+<Callout type="info" emoji="👷">
+For the shielded expedition, it is important to remember to add the `--memo` flag to every transaction. The memo should be filled with the `tpknam` submitted at the shielded-expedition registration period.
+For example `namadac transfer --source me --target you --amount 10 --token naan --signing-keys my-key --memo tpknamq1337mypubkey1964qqqqqq`
+</Callout>
+
 The `balances.toml` file is located at `https://github.com/anoma/namada-shielded-expedition`.
 
 - Namada Shielded expedition 1: