You can use advanced operators to locate login pages on website:
If you have authorized access but forgot the URL, you can find it through your back-end tools: how to find admin panel of a website
Admin panels sometimes live on subdomains like: You can use advanced operators to locate login
When standard paths are hidden or changed (a practice known as "security through obscurity"), security researchers use several methods to find them. Exposed Admin Panels - ThreatNG Security how to find admin panel of a website