reinstalling eM Client

There is a problem with my computer, everything has to be deleted and I have to reinstall windows 10. Then I have to reinstall Em Client. Because I noticed that some users had problems when reinstalling em client I’d like to ask you some advice. What is the address where in can download and install the newest version of the software? How can I transfer contacts and email messages from the old to the new version? Do I use the export button? Should I use the export settings button? I s there anything else I should take care before reinstalling em client? Any advice would be much appreciated.