I know how to kinda do the timing but when i have the timing light on the marks i dont know which mark is suppose to be the 4 deg tdc.

Your auto's spec sheet should tell you what your timing degree should be. For example, a 1969 Ford 429, 6 Degrees BTDC @ 550 rpm in drive gear - with automatic trans, with a firing order of 1-5-4-2-6-3-7-8. All this means is that you want to line up the pointer on the timing light with the 6° timing mark when the engine is idling in gear at 550 rpm. As you can see, it also says something about "BTDC" for this Ford. There is also an "ATDC." "Before Top Dead Center" and "After Top Dead Center" - top dead center is the point where the piston reaches the highest point in the cylinder and that is when the compression is the greatest. Now, your timing marks with have a line labeled "0" with marks above and below it, and depending on which way the wheel rotates, you will see the lines before the "0" (BTDC), or after the "0" (ATDC)