Hi, i have a www.master.com and installed joomla and multisites extension, its all running ok. After I registered a domain name www.slave.com and configured in my hosting services to point(location /webspace/httpdocs), its the same of www.master.com.

Im NOT created nothing im joomla Multisites manager yet.
1 - In na web browser I write www.master.com and show my master page normally. when I write www.slave.com, show me a page of my hosting server about apache etc., when i write www.slave.com/index.php, show me the same of www.master.com. Is it means thats OK to proceed to next step?

No that does not seems OK.

You say that you have create a synonym in your hosting server to delcare your slave site to use the same directory than the master domain.
So normally, you as long as you have not defined the slave site into JMS, you should see in both case the master website and not something with about apaches etc.

As I see the word "httpdocs" in your URL, perhaps that you are working on Plesk and have defined the slave.com as a Domain Alias of the master.com.
If this is the case, you should see both the same master website as long as the slave is not defined in JMS Multisites