# Using expressions in personalisation

With expressions you can create dynamic personalisation fields for your messages.

> [!NOTE]
>
> To use a saved expression from FastStats, you must first create and save one in FastStats. See the FastStats help content for expressions.

To use an expression in personalisation:

1. In your campaign journey, go to the message step where you want to add personalisation.
2. Expand the **option menu**, then click **Edit**.
3. Under **Personalisation**, click **\+ Add Content Field**.
4. Select **Expression** from the drop-down menu.
5. Enter a name for the content field (e.g., *Age Years*), then click **Add**.
6. Under the new content field, click **\+ Add Expression**.
7. Choose whether to **Search** for a saved FastStats expression or build a new expression.
8. If building a new expression:

   - Click the **Expression** tab.
   - Choose a **Table** (e.g., *People*).
   - Enter your **Expression**.

   > **Note**
   >
   > Orbit automatically validates your expression logic and won’t apply any invalid expressions.
9. Click **Apply**.

Your expression is now included as a column in the campaign’s output file.

> [!NOTE]
>
> You cannot view the expression in Orbit, but it will appear as a column in the output file.