Code:
|\
| \
A | \ C
| \
|___x_\
B
The best thing to do will be to post the problems here that you are struggling with, but I can fill you in on the basics.
Observe the triangle above.
C is the hypotenuse of the triangle, and $\displaystyle x$ is the angle opposite side A.
Sin
The sin of an angle is equal to the side opposite the angle, divided by the hypotenuse.
$\displaystyle sin x = \frac{Opp}{Hyp} = \frac{A}{C} $
Cos
The cos of an angle is equal to the side adjacent to the angle, divided by the hypotenuse.
$\displaystyle cos x = \frac{Adj}{Hyp} = \frac{B}{C} $
Tan
The tan of an angle is equal to the side opposite the angle, divided by the adjacent angle.
$\displaystyle tan x = \frac{Opp}{Adj} = \frac{A}{B} $
You have to know these identities by heart.
Post questions of specific problems you do not understand too.