Any tips to get my steering wheel all the way on?

The wheel in the OP photo is a 1969 DeLuxe steering wheel. The only difference in a 1970 DeLuxe wheel is the 69 wheel has a smooth rim and the 70 wheel is pebble grain (better grip?). If you had a standard wheel (3 spoke, center round horn button), and didn't change the horn mechanism, that's why it doesn't work. The mechanisms are very different. Do you by any chance have a picture of the horn mechanism? I can tell you right away if you have the right one.

If the blue wheel is like your original wheel, is your car a GT or Custom? In 70 that type of wheel was standard with the Dart Custom and the GT as a part of the "high trim level" - VIN starts with "LH". Those same wheels were the DeLuxe steering wheel on B- Bodies in those years.