If you mean that you have a Full Backup taken a few months ago, then to Restore that backup you should open Acronis and click on Backup and Restore, then choose the Restore option and follow the on-screen prompts.
By doing this though, you will be restoring your drive to exactly as it was at the time of making the image. Anything installed after the date of making the image, will be lost and would have to be re-installed.
I make regular full backups on a fortnightly basis. If I made frequent changes to my programs etc, then I would make more frequent backups.