When you are done with reassembly and start to analyse the source, the SYMBOL directive might become useful. You can replace any label by a symbol name of your choice, by specifying a name and the program offset.
A good example for this tutorial might be Great Giana Sisters, which I reassembled and analysed 10 years ago for fun. It also shows how do deal with a raw binary program, starting at $1000 with program entry at $102c. In the config file you see that I have lots of PTRS directives to define program addresses (which are otherwise no known to the reassembler) and all my symbols which I added during analysation of the code.
The ripped binary (from a cracked disk):
https://server.owl.de/~frank/download/gianacode.1000
The config file:
https://server.owl.de/~frank/download/gianacode.cnf
The reassembled source:
https://server.owl.de/~frank/download/gianacode.asm