If so do I leave it as an abbreviation or put in the whole name?
Please share your batch code. It's the seven digit combination in brackets at the top of your screen that looks something like [AAA1-BC8]
That is an abbreviation for William. In most projects we do not expand abbreviations of names, we just type what we see written. Different projects have different instructions and that is why erutherford asked for the batch code. That way he can double check the instructions and make sure you get the correct answer.
Read the project instructions and the field help for 'given name' field. I t will say to either expand abbreviations or do not expand abbreviations.
For given names, we do not expand abbreviations because "Wm" could be "William, or in older records, it could be "Willum" depending on the geography of the project -- both names are common in the 1700-1800's particularly in the southern US. Notice that British projects rarely abbreviate names