I grabbed some custom JavaScript from a previous post to do mine.  For the field you want to add the tooltips to you need to put checkboxcss in the CSS class under "Advanced".

//Script to add tooltips to specific checkbox values

$(document).ready(
function() { 
 var label=$('.checkboxcss .cf-field label');
  label[1].title="Answering phones, making copies, minor filing/data entry, assisting with product inventory, etc.";
  label[2].title="Painting, minor repair, cleaning, etc.";
  label[3].title="Invasive species control, controlled burning, Prairie seed collecting/processing, tree/shrub/plant planting, etc.";
  label[4].title="Registering campers, wood sales, daily restroom cleaning, staffing entrance gate, fielding general questions, monitoring grounds for trash, reporting any issues to staff";
  label[5].title="Riding the horse trails (must have own horse) and monitoring for any misuse or dangerous conditions and reporting to Park Manager";
  label[6].title="Chaning oil, sharpening mower blades, servicing chainsaws, minor mechanical tasks, etc.";
  label[7].title="Mowing, weed trimming, pruning, picking up trash, etc.";
  label[8].title="Assisting with the grooming of the cross-country ski trails.";
  label[9].title="Miscellaneous woodworking projects";
  label[10].title="Leading public environmental based educational programming, promoting Olmsted County Parks at public fairs/booths, etc.";
  label[11].title="Assisting with the daily diet prep of the zoo critters as well as cleaning the enclosures, enrichment of animals, record keeping, etc.";
  label[12].title="Answering phones, staffing the front desk, fielding questions from zoo visitors, renting skis/snowshoes, minor data entry, etc."
});