I have described this procedure a few times before if you can find it on a search but anyway here goes.
You need to work out where your beading is going to go first then mark a line round the arch with a good quality indelible marker. Trim the lower section of foam so it fits about 1/2" away from this line all the way round and down to the parcel shelf and to the rear upright angle for the tank board. The other piece which is rectangular then needs to be trimmed to fit from 1/2" the other side of the marked line and to the inner wing all the way round the arch. Glue the foam down with the minimal amount of glue. Then turn the arch trim inside out and glue the beading only down to the marked line. Make sure the glue has gone off well then you can pull the lower section down and only glue it around the waste edges and not on the foam at all. Once this is done (You will probably need to trim it and add some slits where it goes over the forward edge of the parcel shelf) then do the same on the upper outer section, again do not glue onto the foam only the outer edge. doing it this way means the bit over the foam "floats" and so you get the proper padded effect.
Use a good quality contact glue like Dunlop one from Woolies trim.