Did one last week in wifeys 307.
It is a small halogen bulb. It is not a common size so you need to sort out the right one. Buy a spare too!
Dipped beam is the light behind the glass ball type light.
In the engine area there is a round access hole, like a big lid on a jar.
Electric connection just pulls off.
There is a sprung bit of wire (fat paperclip wire) that holds the bulb in and then hooks over an edge, this needs to be unhooked and springs back, with bulb then coming out.
Bulb sits in plane and wire clip holds it in. As above - don't touch the glass of the bulb.
I think
Halfords will do the fitting too for £5 if you are not confident.