1. Free download Leawo MKV Converter here, install and initialize it. You will find the start-up interface with getting started manual.
 

2. Press the "Add Video" button to add video files, or directly drag the files in from the file browser. The imported files will list under processing order. You can modify the output file name, play the media file and take some screenshots. 

3. Select an output profile. Click "Settings" button to change conversion settings. 

Change codec parameters, e.g. Video Codec, Bit Rate, Video Size, Frame Rate, Aspect Ratio, Sample Rate, etc. to get the output video in desired quality and file size.
 

4. Upon the "Video Edit" panel, there are some powerful functions to help you make the video better.
a. "Trim". Drag the triangle limiters on the player bar or input the precise time value to trim video length. 

b."Crop". Select a crop style from the "Zoom" dropdown box or change the dashed-frame on the player window to crop the video frame.
 

c. "Effect". Set video brightness, contrast and audio volume,etc.

d. Watermark
"Logo". Import an image as a logo watermark, use the controls to change its position, size and transparency.

"Text". Enter a text and assign the desired font style to generate a text watermark on the video.

5. Return to the main interface and click the Start button to start MKV video conversion.