The most basic circuit, assumes a constant 50 ohm source resistance and constant amplitude from the generator.
Connect the generator directly to the coil. Tee this connection off to the voltmeter. Sweep frequency while measuring voltage.
You don't measure phase this way, and must reconstruct it from a curve fit, or the Kramers-Kronig relations.
This is a shunt method, and works best for impedances less than 25 ohms.
You can also do a series method, where the coil is in series between source and load; in that case, replace the tee with a coupler (tie the grounds with a much lower impedance, e.g., a metal box with two connectors bolted into it) and connect the coil between the center conductors. Terminate the voltmeter end so that the system is 50 ohms all the way through. This works best for impedances more than 100 ohms.
You can measure phase this way, but you need a reflectance bridge. A VNA (vector network analyzer) contains one of these each for both source and load, and measures phase (hence "vector"). This also lets you determine any line-to-ground impedance the coil may have (which can be substantial when high impedances are being measured).
Tim