Potty Training Advice!?

I've just started potty training my 2 year old. When we're at home and she has her nappy off I can usually tell when she wants to wee/poo so when I ask her if she wants to sit on the potty she will do and use the potty. I'm not sure what to do when we go out though to start with - do I use nappies/pull ups or put little knickers on her? I tried the knickers once at home but I think she thought it was a nappy because almost immediately she wee'd in them! I don't want her to have lots of accidents in her knickers while we're out but I also don't want to confuse her by swapping between nappies and using the potty! I'm trying to stay home as much as possible for these first few days but inevitably I need to pop in and out sometimes. I need advice please!!