Well, you have some work to do. You first need to discover the when and where of your ancestors. When did they emigrate and where did they live (and when did they live there).
If you know when the arrived you might be able to find the passenger list. Depending on the time frame, the list may name the village they came from. You can usually get a time frame for emigration from the 1900 and 1910 federal census (and maybe the 1880 census). Ancestry.com is a good place to search these records (if you have a subscription) otherwise you can try your local library or a LDS Family History center (which are open to the public).
If the passenger list gives no clue, I would then try to learn what church they attended. You can learn what township they lived in from census records and plat maps - if they owned property. There are some plat maps on the Manitowoc County genealogy website. Once you know the township, you can look for churches that were nearby (keep in mind there maybe more than one church to consider). If they attended a Catholic church most of the church records are available from the diocese archive in Green Bay - you can search these records if you visit there. If you live in the Manitowoc area you might go directly to the church and ask if they will help search their records (usually you give them a modest cash donation).
I have found village names in marriage, baptism and death records - both in church records and sometimes in civil records (especially civil death records - again, depending on the time frame).
If that doesn't work out, try to find when he was naturalized. This can also be found on the census records. If you know the year you can contact the library at the University of Green Bay (which houses the declaration of intent and naturalization papers for Manitowoc County). They will search for these documents, usually in a 10 year window for a modest fee.
Hope this helps,