Update FULL_HELP_DOCS.md

FULL_HELP_DOCS.md

@@ -119,7 +119,7 @@ Get Id of builtin Soroban Asset Contract. Deprecated, use `stellar contract id a
 * `--rpc-url <RPC_URL>` — RPC server endpoint
 * `--network-passphrase <NETWORK_PASSPHRASE>` — Network passphrase to sign the transaction sent to the rpc server
 * `--network <NETWORK>` — Name of network to use from config
-* `--source-account <SOURCE_ACCOUNT>` — Account that where transaction originates from. Alias `source`. Can be an identity (--source alice), a public key (--source GDKW...), a secret key (--source SC36…), or a seed phrase (--source "kite urban…"). If `--build-only` or `--sim-only` flags were NOT provided, this key will also be used to sign the final transaction. In that case, trying to sign with public key will fail
+* `--source-account <SOURCE_ACCOUNT>` — Account that where transaction originates from. Alias `source`. Can be an identity (--source alice), a public key (--source GDKW...), a secret key (--source SC36…), or a seed phrase (--source "kite urban…"). If `--build-only` or `--sim-only` flags were NOT provided, this key will also be used to sign the final transaction and the secret key must be passed or available in the key config.
 * `--hd-path <HD_PATH>` — If using a seed phrase, which hierarchical deterministic path to use, e.g. `m/44'/148'/{hd_path}`. Example: `--hd-path 1`. Default: `0`
 * `--global` — Use global config
 * `--config-dir <CONFIG_DIR>` — Location of config directory, default is "."