Well, I created the account and then created the Zymic Mysql, I upload the data to Wordpress 2.8, I put the permissions but still the message of

Error establishing a database connection
This either means that the username and password information in your wp-config.php file is incorrect or we can not contact the database server at localhost. This could mean your host's database server is down.

* Are you sure you have the correct username and password?
* Are you sure that you have typed the correct hostname?
* Are you sure that the database server is running?,

My site is: www.goiabasassassinas.vndv.com

Database User: goiabasassassinas_user
Databas Name: goiabasassassinas_sql





What do I do?

Sorry to burst your bubble but with that domain name you're getting nowhere!
Unfortunately mySQL usernames on zymic over 16 characters don't work (and may be the same for tables) and considering your account name is over 16 characters before even adding _"username" you are totally in a crap state of affairs. Make a new account with a shorter name.

If you can't get a name short enough that you want there is always the option of buying the domain name you want (you can purchase this from any company and some are pretty cheap too) and have it directed to the zymic hosting I.P. of your shorter named account on zymic.

Hope I've helped!