First: you need to install your Desktop Manager (latest is 4.1) from
https://www.blackberry.com/Downloads...B9D5EE16489088
Step 2: Install the Handheld software -- in your case, select 7510 from the same pull-down menu.
Follow the screen instruction during the installation.
Note:
1. Make sure you select "Backup Data" option.
2. You may lose some of your pre-loaded application -- so make sure you have the software at handy