Dab using a cloth dipped in a solvent containing n-heptane. Any coloured residue can be bleached with Chemspec dye gone.
If the silicone is only on the surface of the carpet, leave it to harden and then scrape off using a blunt knife. If the silicone is trodden into the carpet, scrape off as much as possible using a blunt knife. If necessary, use silicone remover (although not on carpets containing polyamide). Follow the manufacturer's instructions carefully.