The 155's are a pain to jack up!! My old twinny was damaged by a tyre fitter who messed it up and dinted all the passenger footwell!
There are three possibilities.
1. You should have a protruding jacking point behind the front wheel about 150mm in from the edge of the car. This is for trolley jacks but is not the strongest point, I've managed to bend it before.
2. The small arrow on the side skirt points to a place on the sill where you can use the jack supplied with the car. Obviously use axle stands too!!!
3. Also heard of people using the bottom suspension arms to jack the car, never done it myself though.