Check all parts are present. - You should have seven pieces.
1 x post and rail frame
1 x roof 95 x 50 mm.
1 x rear iron wall 40 x 89
2 x side walls
2 x posts
Remove excesses and file/sand where necessary.
Paint all pieces
Glue posts at each end of rear iron wall.
Glue side walls to rear wall at posts. At this join the heights of the rear wall and the side walls should be identical.
Invert the wall frame on work area. ie, upside down. Take the post and rail frame and place into position. Glue posts to side walls one at a time allowing for the first to set before positioning the second.
Be sure to have the frame as square as possible. Glue roof to walls.