Voltmeter must be connected in parallel into the circuit.

Ammeter must be connected in series into the circuit.

Analogy of circuit and hydraulic system with a pressured pipeline:
Volt:  Similar to the water pressure in meters in the pipeline.
Current:  Similar to the discharge in m³/s in the pipeline.
Resistance:  Similar to the local energy loses in meters in the pipeline.  Energy losses through the wire or pipeline are ignored in these problems.