The material missing from your list is water or some solvent. To test if a sample compound is ionic, you need to dissolve the solid compound in water. Ionic compounds typically dissociate into their constituent ions when dissolved in a solvent, and these ions are what allow the solution to conduct electricity.
After dissolving the compound in water, you can then use the conductivity apparatus to measure the electrical conductivity of the solution. If the solution conducts electricity well, it indicates that the compound is likely ionic, as the presence of free ions facilitates the flow of electric current. If there is little to no conductivity, the sample may be covalent or non-ionic. Thus, water or a suitable solvent is essential for the testing process.