To conduct tax legislative history, you may have to look in more than one place, and understand more than resource. There is no "right" way to go about it, but understanding what resources you have available to you will get you off to a fast start.
Look up the IRC section you need. Federal tax law begins with the Internal Revenue Code, enacted by Congress in Title 26 of the United States Code (26 U.S.C). These can be found through our subscriptions to Westlaw, Lexis, or Bloomberg Law, but can also be found through the IRS website.
Find the credit for the section. Note Public Law numbers (ex. P.L. 98-369) and dates.
Look for an already compiled legislative history for that section or P.L. See Legislative History Resources on the left for links to these histories. If no compiled history already exists, look up the P.L. number to find any bills, committee reports, etc. associated with it. You can do this by searching for the P.L. on Congress.gov, or through a subscription database such as ProQuest Congressional (UST login required).
Focus on documents in order of their importance (and remember these cannot be cited as precedent, only explanatory):
Look at other documents from the IRS for context, decisions, and guidance. A table of sources for IRS Materials can be found here.