Michael.
Hi, an ammeter is placed in series with the main power lead, that means all power [ in amps ] goes through the meter. The wire has to be large enough to handle the total output of the alternator so a # 4 wire is a good choice as it will have very little resistance. A smaller wire like # 12 will have more resistance and heat up.The ammeter will go in the circuit between the battery and main fuse panel.
A voltmeter is placed in parallel or across the battery to measure voltage.
Hope this helps,
Perry.
