ask your parents, grandparents or who ever of your closer family is still alive for names, dates, places, occupations etc.. Ask them for vital records, letters, diaries or other papers, which could provide concrete dates or hints for their lives.
Go, for example, to
Create an account. It is for free! Got to the SEARCH section, put names and information there and hopefully get a start.
Other pages would be www.ancestry.com or www.myheritage.com, but they are not for free.
All the following depends on the origin of your ancestors, because many countries have their own archives with more information, for free or for a fee.
Dear Ms. Moore,
Thank you for posting your request on History Hub!
For an overview on how to begin your research, we suggest that you review NARA’s Resources for Genealogists, as well as the FamilySearch Research wiki for United States Genealogy. In addition, the document Suggestions and Advice for Family History Researchers may be useful.
We suggest that you also begin by talking to your various family members, especially the more senior ones, and ask them questions so you can gather names, dates, places, and stories. With that information in hand, you may begin to gather records about these family members and the places associated with them.
We hope this is helpful. Best of luck with your family research!