Pradeep Prajapat You need to find the value of dielectric loss (it is considered as the imaginary value). And then taking the ratio of E''/E' you can get tan delta.
Apart from mathematics of the equation, the real part (epsilon)' is dielectric strength or the manitude of insulating nature while (epsilon)'' denotes the loss of electrical energy.
If you have an LCR meter and parallel plate capacitor (prob) than you will get the value of Cp and Rp, using this value can calculate constant using equation like ε'=(Cp/C') where C' = (εo*Π*r2/t) t=thickness of a sample, r=radius of a parallel plate, and εo = free space permittivity. For Loss ε''= (1/2Π*f*Rp*C').