Feedback and contact
A detailed description of the problem is a good starting point. This should include what is not working (anymore) and since when, and what you where doing at the moment before the problem occured. If the problem concerns a workplace, the hardware ID (e. g. 16-PF123) is helpful.
If possible it is also helpful to document error messages via screenshot: In Windows operating systems, use the print key and copy and paste the screenshot into a image editing program or directly into an e-mail.