Mark the spars with a square and pencil where the ribs have too go.
glue the outer rib and inner rib on with CA using a steel rule as a square, take some time to get these 2 right.
now just insert the other ribs using the pencil marks and it should all work out, you can double check using the rule as a square.
If it's all balsa constructon you can use CA on the lot if theres ply or hard wood involved tack with CA then use PVA.

Have a look at www.spadtothebone.com for ideas for your next plane