Have to keep putting oil in your peugeot 207?

Continually needing to add oil is a sign of a mechanical problem. If there are no obvious signs of an external leak (like an oil stain under the car when you park it), most likely the problem is that the oil is getting into the combustion chamber and being burned.

Either way, if you don't know how to fix it yourself (and if you need to ask the question, trust me, you don't know how to fix it yourself), you should take it to a mechanic and have it examined.