Hi Cindy thanks for posting in the Lucid Community! You can adjust how your flowchart prints using several options in Page Settings which you can access by choosing File > Page Settings. 

First set the size of your page to the equivalent paper size that you'd like to print on under the Page size option. In my example below I've chosen a standard letter size. Next choose Fit to page which will automatically resize your entire diagram to fit that page size. 

From there you can print your diagram! Give this a try and let me know if you have any additional questions.