'''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
If your Campy front derailleur is a braze-on type (i.e. there is no clamp as part of the derailleur but there is a separate adapter clamp that it bolts to) you can use the adapter to mount your Tiagra . If the Campy fd has a built in clamp, you can't switch it over to the Tiagra.
You apparently bought a "braze-on" style Tiagra and will need a separate adapter clamp to use it. Any LBS can sell you the right one.
Just make sure to get the correct size clamp. There are three, 28.6, 31.8 and 34.9. If your not sure, look inside the Campy clamp, it may be labeled as to what size or just bring it to the bike shop with you, they'll be able to tell you what size clamp adapter you need.
At least Shimano has figured out the elusive "part number" concept. If you call Campy looking for a hub cone, or other necessary small part, you are inevitably asked "what year?". Thanks fellas.....that's a big help when I am working on someone's bike covered in parts from various Campy groups scrounged from ebay.....