You're doing great! :-)
That's quite an intricate marriage certificate! Thanks for uploading these photos.
I went ahead and added the reference I found to the profile for Elvira Hatch. The link that is in the source will take you to the FamilySearch site where I found the information.
What I like about FamilySearch is that when you look at a source page, at the bottom of the page it gives you the exact paragraph that you can use to cite the source. You can see that I just copied & pasted this paragraph into the profile. This also contains the link back to the source on FamilySearch.
This is how you start stitching together a the background of your family.
Now with what is on the profiles so far, this is how I would go about doing further research. Others may have different or more suggestions.
First, your immediate goal is to find more about William J. Hammill. Sometimes it's challenging to do direct search. So we have to do it indirectly by finding out more information around the person.
* You uploaded a photo of the divorce notice. There are 3 minor children listed. You currently only have one son listed, Clifford Hammill. Who were the other two? What are their birth dates?
* I go to Clifford's profile, and the biography says he was born in 1896. This was before William and Elvira were married. He would be about 4 years old during the 1900 Census. You can use FamilySearch to see if you can find them in Minnesota. If any of the other children were born before 1900, then they will probably be listed too in the 1900 Census.
* I see that there is already a reference on William's profile to the Minnesota state Census in 1895. You can go to this reference in FamilySearch, click on Elvira, and then copy & paste that citation to her profile. Then do the same for Charles. These are great sources for them too.
* It seems that Minnesota does a state census in between the US Census. Can William and Elvira be found in a Minnesota State Census in 1905? Was a state census done then? Were they still married at the time that Census was done? I see that they divorced about 1905. Do you know when that divorce happened?
* Did William stay in the area, or Minnesota afterwards? Can he be found in the 1910 US Census in Minnesota? Or does he just "disappear"? If he stayed in the area, did he remarry? If so, then you can search for Marriage Records in Minnesota.
* William was born about 1866 in Michigan. Can he be found in the 1870 US Census in Michigan? Or found in the 1880 US Census? It may be hard if there are multiple matches. His names are not so unique that it's easy to spot a match, but oftentimes you can infer the right person based on approximate birth year, and location. If you can find a good match, that it's likely him, then you can possibly find his parents and siblings, and then this is a good starting point to the rest of his family tree?
Hope this helps you think of questions to ask and ways to approach the research.