I have an android phone and here is how I do it

ON the up app on the top left corner is a symbol that looks like 3 lines - click that and then on the list look for Apps and then just follow the instructions that are given.

Here is a website that explains how - http://www.tomsguide.com/faq/id-2361176/syncing-jawbone-up24-myfitnesspal-food-data.html

Hope this helps