Normally if you create edit logo using any basic drawing tools like microsoft paint or something the transparency will be lost.
Today, for doing this operation you can use Adobe Photoshop as a medium you can download photoshop from publisher’s website or by Google search
How To Do It ?
Install and Open Photoshop
Now Click on Open
From the selection windows choose the particular file you want to make transparent
Now from layer’ window right click and select the option “Layer from the background” then click OK
Now select Magic Wand Tool
Using This tool click inside the image were you want to make it transparent and press delete button in the key board
Once done you will see some check boxes instead of the replaced color
Now as normal save your image by click save as option from File menu
Do remember only save the image as .PNG format as it only supports transparency