I had my computer worked on and lost the download. How
do I reinstall without having to renew or buy it again?
Good to know what is your F-Secure solution and your OS / system / device.
But just as a generic suggestion:
-> possible to download installer OR to open My F-Secure Account portal (for F-Secure TOTAL or F-Secure SAFE solutions) from there:
-> need to know your licence / subscription code / activation key. Or to use your credentials for My F-Secure Account. Most likely, should be possible to find it under your mail-letters, boxes or to recover password for Account.
Otherwise, another option is to contact their official F-Secure Support Channels (for example, chat):
-> installation guides possible to find there: