Detail of visa application procedure you can find here. Please read this document carefuly.
The completed EXCEL Form with the personal data is to be provided strictly in EXCEL format and e-mailed along with a scan of the data page of the passport to email@example.com.
Download form here.
Important to remember:
1. Make sure that each passport has two blank visa-designated pages.
2. Make sure that the expiry date of the passport is at least six months after the last day of the expected stay in Russia.
3. If the passport does not meet these two requirements, a new passport must be obtained or the existing one is to be prolonged before you can request the invitation letter.