There are a few different places to look for legislative history documents on Lexis. Lexis has a few different compiled legislative histories available for select major federal laws, as shown in the picture below. To access these histories from the Lexis main page, select "Statutes and Legislation" in content, and then select "Federal," as the content type. As you can see in the picture below, Lexis also has other legislative history documents available, such as committee reports.
However, if you are interested in the legislative history documents for a law not listed above, you must find the particular section of the U.S. code that you are interested in exploring on Lexis. If legislative history documents are available on Lexis, they will be along the right-hand side of the page for your law under the Bill Tracking link.
If you click on the Bill Tracking link above you will find a variety of legislative history documents including links to the Congressional Record under the Actions section, and links to other versions of the bill under Related Legislative Materials along the right-hand side of the page, as shown in the picture below: