Ok, I am a newbie in the terms of bonus game content and I have literally no idea what to expect from the 2 free DLCs I just installed, and I hope it justifies the pathethic question I have at least a bit. SO i Download the packs, install them, launch the game... And now what? I Guess there is a barber somewhere and the armor I have to find myself, it's not like it's just going to appear in my inventory, right?...

Armor set is on a vendor in the first village. It's not free (100-300'ish oren for each piece), and you need to be level 4 or 6 (can't remember) to equip it.

Hairstyle would make sense to be on a barber, but I haven't found one yet.

Here's the sticky thread about activating the DLCs and some additional discussion.
https://www.gog.com/forum/the_witcher_3_wild_hunt/guide_free_dlcs_activasion

Haircuts are indeed supposed to be available due to a barber.