Windows Media Player is the standard audio and video player for all Windows-based devices. And while it's more than enough to play all major audio and video formats, the process of connecting external subtitles is not that easy. You will either have to change the external subtitle file or insert the subtitles into Windows Media Player through a third party program.
Steps
Method 1 of 2: Rename the subtitle file

Step 1. Move the subtitle file to the same folder with the desired video
Move or copy the external subtitle file and paste it into the video folder to which you want to add subtitles.

Step 2. Rename the subtitle file to match the name of the video
Right-click on the subtitles and select the "Rename" option. Enter the name that was assigned to the video file and press Enter.

Step 3. Open the video in Windows Media Player
Right-click the video and choose Open With> Windows Media Player. If Windows Media Player is the default audio and video player, double-click the video file.

Step 4. Make sure subtitle display is enabled in Windows Media Player
Right-click on the bar at the top of the player, move your cursor to the Lyrics, Subtitles and Captions option and select Enable if available. Close the player and then restart it to enable subtitle video.
Method 2 of 2: Install additional software

Step 1. Download DirectVobSub
DirectVobSub is a popular open source Windows software that fixes a subtitle display issue in Windows Media Player.
- Download and install DirectVobSub from the official download page. The program is available for both 32-bit and 64-bit versions of Windows, so download the version that is supported by the operating system.
- Scan DirectVobSub if you downloaded it from another source. This will tell you if the file contains viruses or malware.

Step 2. Install DirectVobSub
After downloading the installation file, double-click on it with the left mouse button to start the installation process. When the installation is complete, Windows Media Player can display external subtitles without any problems.

Step 3. Rename the subtitle format to “.sub”
If Windows Media Player does not recognize the subtitles even after installing DirectVobSub, you may need to change the subtitle file format. Right-click on the subtitle file, select "Rename" and change the ".srt" at the end of the file to ".sub".