To use the index look for the first letter of the surname you are researching in the alphabet at the top of the page. Scroll down to find the surname you are researching. Once you find an ancestor, you will see a source code that if you hover the cursor over-the publication name appears. You can click on the source for further information. If the source is available online, you will be able to access it from here. Information on purchasing the source, if available, is included. Otherwise, you will have to locate the source at your local library. Below is an example of one source. On the actual website you are able to click on purchase information and available online information and be taken to new pages.
Example: a6m32b Brown, Geo. H. Record of Service of Michigan Volunteers in the Civil War, 1861-1865. vol 32. 1903. [2,383] 28 May 2003 Purchase Info Available OnLine
The names in this index are not necessarily all from Michigan, but are names that can be found in Michigan publications. The publications sources include county histories, Civil War service records, cemetery records, land records, biographies, diaries, census, immigration, probate and tax records to name a few.
I have searched for many ancestors in this index. When I searched my own surname I was surprised to see my husband and two children listed. You never know what you will find with the Michigan Biographical Index, take a look.