How to make amazon affiliate link?

Hi,
Any amazon affiliates here?
I want to know how to add my affiliate associate id to an amazon link.

Suppose my associate id is: abcdef-21

Then how do I add it to an amazon link for proper tracking?
Also, can same affiliate id be used for other countries?
Suppose I signed up at amazon.in, then can I use same associate id on amazon.com, or is that different?
Thanks