Len, as others have said, you need to load your tree into a program that will let you produce small gedcom files.
If your intent is to upload it to WT, you should do a very small upload to get familiar with the process and to determine if your data is complete enough. If your source is Ancestry, likely not. (The shared links will be missing)
Due to the work on WT that is required, don't upload more than a 100 people at a time and try to keep on one branch of your tree so relationships can be maintained.