I have been working on the Family tree maker and have generations of information. I'm willing to share the information with others, but it's time consuming to manually go back and forth to put in the information. The comments that they didn't have it set up yet are from 7-8 years ago
You can tree using SmartCopy (see https://www.geni.com/projects/SmartCopy/18783) to copy that information that is not already on Geni.
Please read https://www.geni.com/projects/Connecting-to-the-Big-Tree/17983
You can also make a GEDCOM download and upload that to Geni, but that will create many duplicates and merging those may take far longer than using SmartCopy.
If you are going to use the GEDCOM method it may be wise (if you can manage that) to use separate GEDCOMS for those families you want to import and not import any families that are already on Geni. Geni will give you the means to make a GEDCOM download from any profile you added to Geni. So it may be wise to add a few profiles by hand and make a GEDCOM export to see what is already on Geni. Keep in mind that if you have profiles without a date those will probably be private on Geni (so other Geni users can only see they exists, but cannot see any information about them). So please add at least a date estimate to any profiles you want to add to Geni. Please also read https://www.geni.com/projects/What-to-do-after-you-have-uploaded-a-GEDCOM/53094 (it may be useful to read it before doing the upload). If you use a GEDCOM import please do NOT import the same GEDCOM more than once. Each import will create duplicates that have to be merged by hand!
If you need further assistance and are a Geni member you can ask for help on https://www.geni.com/discussions/192543