From your question I am assuming you are fairly new to Genealogy, at least to Wikitree.
Build a profile for your grandfather, and any other family members you have information on.
What is now available in WIKITREE is a research tool called RootSearch. Scroll down the right side of the profile for which you want to gather more information to Research>RootSearch. Click on it and you will get a page with all the pertinant date pre-loaded. Then at the bottom of the page, click on a search site, usually I try Google first. You will then get a selection of data sources that may or may not work for you. Then try Family Search, LDS, Salt Lake City, Utah, or others.
In either case or if you use the other sites and you find an applicable source, or one that looks close, copy and paste the data to your Wiki profile to the proper space i.e., Biography, Source, Reference, etc. Just get it there, you call always edit later.
Be sure and cite the source, and include the URL link so someone else can follow your research. Remember, the site of a relative may give you the information you need.