Applied for Philhealth, SSS, and Pag-Ibig months before I had my JO, what about my contributions?

Last May, before graduation, may pumuntang Philhealth sa school namin and they encouraged us to open an account so nag register ako as voluntary member but till now hindi ko siya hinuhulugan. This January ay magpapasa na akong ng reqs and magsstart na din mag-work. Kailangan ko ba hulugan yung May-Dec ko or magsstart yung contribution ko once I started my work na? Is it the same ba with SSS and Pag-Ibig?