Adding sand will not work.  https://www.uaex.uada.edu/farm-ranch/crops-commercial-horticulture/horticulture/ar-fruit-veg-nut-update-blog/posts/adding-sand-to-soil.aspx

First, start by taking a soil test to see what you need to do to grow plants in that soil. Do not skip this step. UMass has a soil testing service; here is a link https://ag.umass.edu/services/soil-plant-nutrient-testing-laboratory/ordering-information-forms to the information you need to submit a sample. 
Here is the test to use: aRoutine Soil Analysis - Order Form for Home Grounds and Gardening 
After you have the results, let us know if you have any questions about how to proceed, based on the test results/recommendations. 

Next, the remedy for loosening clay soil is add organic matter into the soil on an annual basis.

"Solution: Due to its unique composition organic matter added annually in reasonable amounts on the soil surface or tilled into the soil can help improve soil structure resulting in improved drainage properties of all soils. Clayey soils will have improved drainage characteristics and sandy soils will be able to hold more water when compost is added at regular intervals. Organic matter has the added benefit that as it breaks down it will contribute nutrients to the soil that can be taken up by plants. This is particularly important for sandy soils which have low natural fertility levels. Organic matter also contributes to “feeding” the soil microbiome." 

Finally, you can make your own organic matter by creating compost. Here's some information and links to get you started. https://composthq.com/composting/how-long-does-it-take-to-make-compost/