Hi Ted. To figure out the locations of the nails and where to drill, perhaps this picture will helps:
View attachment 435242
The nails are intended to strengthen the construction. Then they are on either side of a connection.
On this picture I transferred the connections of the parts of the front frame in blue lines to the rear part of the frame. You can mark them with a tiny lines of a pencil on the wood and rub them out later.
Now you can position a nail on both sides of all connections. At the distance of the connection that you finds visually the most attractive.
At the foot of the fork it is up to you to determine where and how many nails you want to place.
Do you like to put extra nails in-between, no problem. You are the captain, it's your BN.
You can drill all through, but you can also make the marks on both side and drill small holes on both sides.
Hope this will help you.
Regards, Peter