When you have your siding cut to the appropriate spacings for the dollhouse scale you are building, glue it in place with woodglue. To create an aged wood finish, use the vinegar/steel ageing method. You may need several coats to achieve the finish you wish.
If your basswood siding begins to warp or curl, lay your facade flat, with the siding face down, and weight the facade down with tin cans to keep the siding from warping as the aging solution dries.
You should also trim some of your shingles to one inch by ½ inch to use for the front facade and cut your batten strips to length and age both the strips and the shingles before you proceed to the next step.