What is the most logical next event?

How to install a chimney liner
Inspect the chimney.
Use a light source on a string (or an inspection camera if you have one) to look for bends, or restrictions that could interfere with pulling the liner through.
Determine the correct diameter of the liner.
If for a wood stove/insert, consult the owners manual for proper sizing. For an open fireplace, look for a chart or calculator online.