Okay, to take stuff one by one:
The bones you see lying around are, I assume, human-shaped? If so, those are dead character bodies, and you can't use them for bones. If you find an *animal* skeleton lying around you can loot those for bones (right click on them), but not the humans.
If you're still this new, you don't want to hunt foxes or boars yet. In fact, you want to stay as far away from boars as you can, since they randomly might attack you, and may kill you outright. (Which means starting a new character, although you can inherit from the previous one.)
For bones, animal meat, etc., you'll want to stick to rabbits and chickens until you at least learn the ropes and get a few stats/skills built up. To do that, make sure you buy the Hunting skill, then find a chicken or rabbit (rabbits can be randomly most places, chickens are on grasslands, moors and heath), get as close as you can (really, on top of the critter), then right-click on it, when you have a square of four spaces in your inventory, and it'll pick up the animal. Then you can "wring neck" to kill it, then butcher it.
For string, your best bet is to buy the foraging skill (Oral Tradition first), and raise your perception*exploration score a few notches by buying some exploration points, then as you wander you should start finding stinging nettles and spindly taproots, which you can use for string (although nettles can't be used as fishing line and, um, something else, I forget what.)
To help out, you might wanna read over some things (like the foraging tables, combat system, etc.) in the wiki:
http://ringofbrodgar.com/wiki/Haven_and_Hearth_WikiHappy hunting!