The lightcurve should be a simple ASCII file in the "JD mag", "JD mag mag_err", or VaST format. The Catalina Surveys .csv files are also supported. The lightcurve may contain comment lines. Note, that (unless the Catalina Surveys .csv file is supplied) the program expects time to be expressed as a full JD, not MJD. If MJD (or any other form of truncated JD) is used in the lightcurve file, the labeling of plots will be incorrect. Also, the Heliocentric correction cannot be applied to such lightcurves. Example lightcurves may be found here, here, and here (links to data files are at the bottom of these pages). Two period search methods are currently implemented. One is based on Lafler & Kinman (1965, ApJS, 11, 216) paper. You may find a simplier explanation of this method in Russian here. The other is Deeming (1975) Discrete Fourier Transform (DFT) method (see also the discussion in this paper).