Installing an unsigned executable on macOS can be a bit tricky due to macOS's security features designed to protect users from potentially harmful software. Here's a general guide on how to do it:

1. **Download the Executable**: First, download the unsigned executable file you want to install.

2. **Locate the File**: Use Finder to locate the downloaded file. It's often in the `Downloads` folder unless you specified a different location.

3. **Attempt to Open the File**: Double-click the file to open it. macOS will likely show a warning that the file cannot be opened because it is from an unidentified developer.

4. **Override Security Settings**:
   - **Option 1: Open via Context Menu**
     - Right-click (or Control-click) the file.
     - Select `Open` from the context menu.
     - You'll see another warning, but this time there will be an option to `Open` the file anyway. Click `Open`.

   - **Option 2: Allow Apps from Anywhere (Temporarily)**
     - Open `System Preferences` and go to `Security & Privacy`.
     - Click the lock icon in the bottom left corner and enter your password to make changes.
     - Under the `General` tab, you might see a message about the app being blocked. Click `Open Anyway`.
     - If you don't see this option, you can temporarily change the setting to allow apps downloaded from `Anywhere`. However, this option is not available in the latest versions of macOS by default. You may need to use the Terminal to do this:
       - Open Terminal and type: `sudo spctl --master-disable`
       - Press Enter and provide your password.
       - This will allow you to run apps from anywhere, but it's recommended to re-enable security by typing `sudo spctl --master-enable` after installing your app.

5. **Use Terminal (Advanced Users)**: If the above methods don't work, you can use the Terminal to run the executable directly:
   - Open Terminal.
   - Navigate to the directory where the file is located using the `cd` command.
   - Make the file executable by typing: `chmod +x filename`
   - Run the file by typing: `./filename`

6. **Check for Updates**: Sometimes, developers will sign their apps later. Check if there's a signed version available to avoid these steps in the future.

### Important Considerations

- **Security Risks**: Running unsigned executables can expose your system to malware and other security risks. Only proceed if you trust the source of the software.
- **System Integrity Protection (SIP)**: Some steps might be restricted by SIP, which is designed to protect your system. Disabling SIP is not recommended unless absolutely necessary.

If you're unsure about any of these steps or the safety of the file, it's best to consult with someone who has more experience with macOS or to contact the software developer for support.