Install the Sharecaster iOS shortcut
Install the Shortcuts app if you don't already have it.
Click to install the Shortcut App
Once you have Shortcuts installed, download the sharecaster.xyz shortcut.
Click to install Sharecaster
When you share a cast from within the Farcaster app, now you'll see an option in the share sheet to share via Sharecaster.
The first time you share a cast from within Farcaster, you'll need to give permission to share with the shortcut.