You cannot set the default content for the SNS post, but you can set the content for the metadata of the campaign URL.
When the end users share your campaign URL to the SNS network, or post it to anywhere that support to show the metadata, they can see your campaign image, title and description.
E.g. The metadata of a campaign posted in Facebook will look like below:
You can update the metadata of your campaign by following the steps below:
1. Go to Studio website https://studio.brandedminigames.com/ and log in with your account.
Note: if you don’t have an account yet, please check this article.
2. On the top menu bar, select the “Dashboard” button to go to the campaign dashboard.
3. Find the campaign which you want to update the metadata and select it.
4. You will be led to the Game Settings page of the campaign, select “Instant Win Rewards” item on the left menu.
5. In the “Campaign Settings” page, check the “Campaign Profile & SEO” section, you can enter the title, description and upload image which you want to be used as the metadata of your campaign.
6. If the campaign has been published, after updating, please do select the “Save Changes” button on the top right to apply your changes to the campaign.
For more detail about how to customize the campaign furthermore after publishing, please check this article.