Official articles of impeachment are voted upon by the U.S. House of Representatives. Look for House Resolutions and House Reports at Congress dot gov.
You can find them in print in large law or government document libraries and usually, though not always easily, online. Some online Congressional research resources are fee-based databases and some are free.
For example, see previous post from September 26, 2019: What Does an Article of Impeachment Look Like? Read Presidents Nixon and Clinton Articles
For the current Articles of Impeachment against Donald Trump, visit Congress dot gov and search for the following:
H. Res. 755 (and H. Rept. 116-346) and H. Res 767 ( and H. Rept. 116-355):
1. H.Res.755 — 116th Congress (2019-2020)
Impeaching Donald John Trump, President of the United States, for high crimes and misdemeanors.
Sponsor: Rep. Nadler, Jerrold [D-NY-10] (Introduced 12/10/2019) Cosponsors: (0)
Committees: House – Judiciary
Committee Reports: H. Rept. 116-346
2. H.Res.767 — 116th Congress (2019-2020)
Providing for consideration of the resolution (H. Res. 755) impeaching Donald John Trump, President of the United States, for high crimes and misdemeanors.
Sponsor: Rep. McGovern, James P. [D-MA-2] (Introduced 12/17/2019) Cosponsors: (0)
Committees: House – Rules
Committee Reports: H. Rept. 116-355
Many other people and organizations have proposed additional articles of impeachment but, as of today, the above Articles are the only ones that have been voted into law by the U.S. House of Representatives.