You will, of course, need a genealogy software program in which to enter all of your data. Several programs have been discontinued over the years [Ancestry Family Tree, for example.] Some programs offer a free download with basic input ability; the require you to purchase the full-access version. Others are totally free.
Here are a few programs for you to check out:
My Heritage: Family Tree Builder
Legacy Family Tree
Roots Magic [my personal choice]
Mac Family Tree [for Mac users]
My Family Tree
Ancestry.com allows you to create a tree on the website.
FamilySearch.org also allows you to create a tree onsite.
Check Cyndi's List or do a "genealogy software" search for reviews or additional info. Also visit each program's home page.