Collect Logs of Application Web to LEM?

What is the log?  Is this IIS, Apache, Tomcat, other?  What's the log look like?

The Logs is addecuated to RFC 5424  - SYSLOGS format.

And is the IIS.

The application is prepared to generate logs to:

• start Session.
• End Session.
• Fails Attemps.
• Access to specific file.

And that is my question, one time than my web application generate logs and sents to LEM,..... What does LEM to see the application logs and store?

IIS logs don't match the RFC for Syslog, but the LEM does have IIS readers that can parse the IIS logs (this thread gives some details on how to set that up):

IIS 6 & 7 logs into LEM

LEM will read the IIS log text files, normalize them and store them in the Alert Database on the LEM Appliance.

But that are logs of IIS not?

The web application integrate a library "syslogs library for .NET Framework".

If the system is writing syslog to a file or can send syslog to a host, then there may be a LEM connector that matches that data.  Support could help you test your files for a match, or work with you on the process of requesting a connector to normalize your logs.