1. Login into your LinkedIn account and click on clicca sulle impostazioni del tuo profilo.
2. From the dropdown menu choose "Settings & Privacy" (image 1)
3. In this new page, click on "Getting an archive of your data" and then choose "Fast file only" (image 2).
You'll receive an email from LinkedIn with your Contacts File.
4. Open your file in Excel and Save in .CSV format - FORMAT WINDOWS CSV - utf 8 (Windows Comma Separated).
5. Now you can follow the steps in this help article: https://sellf.uservoice.com/knowledgebase/articles/511258
to import your LinkedIn Contacts in Sellf.