Acronis is the software that makes the image for you.
So you install Acronis to your local hard disk containing Windows. You then create a full disk image (clone) of your local disk (which includes Acronis), and save it to your external disk.
When you then restore the clone to another local hard disk, it will copy the local disk at the exact point in time that you created the clone, including the copying of the Acronis software, along with everything else installed and present on that disk.
Its absolutely fine, and nothing to worry about. It makes more sense having it installed to the local disk because once the clone has been restored the software is there. Restoring a clone with the software installed on an external drive could cause you problems.