Junction Block Fuse#1 has +12v with key ON. (Connector Pin#6 below)
Junction Block Fuse#20 has +12v always. (Connector Pin#7 below)
Set meter to DCV (DC Volts). If it has manual range settings, select one greater than 12vdc. (Not needed for auto-ranging)
Touch black lead to any good unpainted chassis ground, bare metal, screw heads, etc.
Touch red lead to each Pin#6, check meter for +12v reading.
Touch red lead to each Pin#7, check meter for +12v reading.
You can also check for +12v on both ends of each fuse, same method.