The M8 gives you caller id on the first 8 lines (those built into the m8x24 cabinet). You must bridge tap the amp fan tail in the same sequence as your lines, blu/wht must be line 1 and go from there in sequence. The two screw posts must go to a digital station port, that is how the M8 gets its power to run and how it sends the caller id info to the KSU to process with the software. Any station port will do, but generally do not use the first one, as that is most handy for the reception phone. Is the Startalk you have may be a Flash?? If so, you will see two phone jacks (4p2c). If you have a 2 port flash, connect jack one to a digital station port. If you have a 4 port flash, connect the other port to another station port. One the first (center) pair on each jack are used, so do not waste space punching down the outer pair of each jack. If you jumper to a regular phone jack and then connect your crossconnect wire, you will use the red-green or wht/blu pair.
You will need to google up a user manual for the voicemail, as you have to program the ksu to do certain things like you do not want lines to appear and ring on the voicemail digital station ports. You may also have to initialize the voicemail (to tailor to your number of digits in your extensions as well as to mate to your ksu. You will have a bunch of reading to do.