How to adjust the ignition timing?

Being a 1996 the timing is not adjustable. It is controlled by the computer based off the base timing. There is a camshaft retard offset procedure, but you need a scan tool to do that as there is no other provisions to adjust it. For that you connect the scan tool. Go to the cam retard offset setting in the engine menu on the Tech II then once there you run the engine up to 1000 rpm and rotate the distributor until the cam retard offset reads withing 2 plus or minus degrees of zero. With zero being "perfect". There are no other adjustments and even the cam offset isn't really needed unless you removed the distributor.

The distributor was remove sometime the engine slow cranking.

Was it running okay and then started the slow cranking or did that start after the dist. was removed and replaced? If it was after, then the distributor could be off on the cam itself. For that you would need to remove the spark plug in cylinder 1. Then disconnect the battery. Remove the distributor cap. Now use a bar and socket to rotate the engine until you can feel the engine come of on TDC on the compression stroke, an easy way to do that is to put a finger in the plug hole and you can feel the compression try to push your finger off. Now if you look on the damper there should be a TDC mark and either a hole or tab on the timing cover near it. Line the mark on the damper with the zero mark. Now look at where the rotor on the distributor is pointing, It should be pointing almost exactly at the post the goes to the cylinder one plug wire on the cap. Be careful though, the flat caps move the locations so be sure of number one location on the cap. If it is pointed directly at the post in the cap it is in time enough that it shouldn't have an issue starting.

https://www.2carpros.com/articles/comprehensive-guide-on-installing-an-automotive-ignition-distributor-step-by-step-process