the monk have several skill in the beginning... like improved unarmed fighting, etc...

I want to know if you have 14 of strengh... will you get a +2 to hit and damage when fighting with your fist?

In short, yes :) The strength bonus to attack and damage applies to all melee attacks. The feats Weapon Finesse and Weapon Focus also apply to an unarmed strike, which make for a pretty tough monk. Just a word of advice though if you're thinking of playing a monk: wisdom and dexterity are *far* more important than strength. As a monk cannot wear any armour (unless they want to sacrifice all their 'monkliness'), the dexterity bonus to AC and the monk's bonus of wisdom to AC are very important, especially at higher levels.

How do you get Weapon Finesse as a monk?

Weapon finesse becomes available to the monk from lvl 3 onwards, regardless of Dex( I think, or you made need dex over 13). Weapon Finesse uses your dex modifier instead of strength to calculate your to hit attack rolls, but you still use your strength modifier to calculate damage rolls.