This question is really complex to answer.

First of all, because of movies and the way "la resistance" is portrayed we tend to think of it as this monolithic entity. It absolutely was not the case. Resistance is in its essence anyone who does subversive acts against an occupier. Like "insurgent", the term itself encompasses a lot of different activities from smuggling to bombings, from hiding people to hunting people, passing on pamphlets etc.

Your question includes 1942, young and politically minded.

I'm going to assume your theoretical person is 15 to 25 years of age and has a political affiliation. Because not being politically minded does not imply you can't be a resistance fighter.

First of all, you do not need to be affiliated with any organized movement to do any of the subversive actions. Plenty of citizens that partook in acts of resistance were just regular people who took matters into their own hands. Such as hiding Jews.

The FFI (Forces françaises de l'intérieur) that was more akin to a well organized monolithic Resistance was not created until Feb 1, 1944, therefore I am not going to mention it. Also, Jean Moulin's CNR (Conseil national de la Résistance) will not come to be until 43-44.

Now as far as political influences you had several (in no particular order and not-exhaustive):

1. The "Milieu", while this is a rabbit hole of its own, the French organized crime was deep into resistance. It is important to know that some families also collaborated, and some played both sides. This choice would not really be politically motivated.

2. Communist, outfits such as "Bataillons de la jeunesse" that joined the FTP (Franc tireur et partisans) in 1942. Those guys had a lot of veterans from the "Brigades Internationales" that fought in the Spanish civil war.

3. Far right and Royalist, while it may seem odd at first glance because far right = nazi amirite guys /s , some members of the far right did not take kindly to strangers invading France, and while a lot of them where pro-Vichy, a lot of them where not fond of being told what to do by a foreign power, least of all Germany in a post Franco-Prussian War and 14-18 world.

4. Socialists could join organisations such as the CAS (Comité d'action socialiste)

There is something important I want to note. As stated in the question, it was relating to 1942. 1942 is still very early for the Resistance and the "Maquis". Moreover, the question is asking about Paris when a lot if not most subversive activities were taken elsewhere in the territory.

Now for "Was obtaining this information easy, or do I need to know somebody to talk to?".

Once again the answers will vary across the board depending on the time and the place. In Paris in 1942, times where incredibly dangerous, the French police in Paris was actively collaborating with the Germans, organizing things like the infamous "Rafle du Vélodrome d'Hiver" aka. " rafle du Vél’d’Hiv" on July 16 and 17 1942 which is the biggest mass arrest of Jews on french soil. Over 13000 men, women and children where rounded up, with the help of 7000 French policemen and hundreds of "activists" from groups such as Jacques Doriot's "Parti Populaire Francais". In a perfume of neighbors ratting out neighbors.

Most resistance groups also had to dodge the infamous "Brigades spéciales" (or BS for short) which was a unit of police dedicated to tracking and destroying resistance cells.

So asking around in 1942 Paris for a Resistance group to join will most likely result in your untimely death after very degrading and cruel interrogations.

Lastly, while the resistance had some politically oriented groups it's also important to acknowledge that people from all walks of life, sex, political affiliations, creed, class etc. helped or joined the Resistance. An estimated half a million French, and also foreigners, risked or lost their lives. And this is the part of that war that we'd rather remember and pay homage to.

Sources:

Cyril Guinet - Occupation : La police française, précieuse alliée du IIIe Reich

Daniel Cordier - Jean Moulin. La République des Catacombes

Dominique Balvet, Jean-Louis Crémieux-Brilhac, Claire Andrieu, Guillaume Piketty, Bénédicte Vergez-Chaignon, Jean-Pierre Le Crom - Dictionnaire historique de la Résistance