Before opening the file, it is highly recommended to upload the APK to a scanner like VirusTotal to ensure it hasn't been tampered with. Install and Launch Locate the file in your folder and tap it to begin installation.
Since you are looking for an older version, you must use a repository that archives previous builds:
Downloading Blued 4.9.3 APK for Android makes sense if you have an older phone, need offline installation, or prefer a legacy interface. However, for the best security and feature set, consider updating to the latest version from the official Google Play Store whenever possible.