Load the file in gimp : File / Open (search file in your folders)
Gimp menu : Image / Transform / Rotate 90° clockwise
Save the file : File / Export As (fill in the name with the extension .TGA)
Change the colors in gimp menu : Colours / (try the different items)
A way to make a Square border : use the 'Rectangle Select Tool', tick 'Fixed' and fill in below 'Fixed' : 1:1
Make a selection, then 'ENTER' on you keyboard (you see maching ants) and then: 'Select / To Path'
Set selection of : Select / None
Select the 'path' dock, you see a layer with a quare path. Right click on this path layer and click on 'Stroke Path'
Gimp menu : Image / Transform / Rotate 90° clockwise
Save the file : File / Export As (fill in the name with the extension .TGA)
Change the colors in gimp menu : Colours / (try the different items)
A way to make a Square border : use the 'Rectangle Select Tool', tick 'Fixed' and fill in below 'Fixed' : 1:1
Make a selection, then 'ENTER' on you keyboard (you see maching ants) and then: 'Select / To Path'
Set selection of : Select / None
Select the 'path' dock, you see a layer with a quare path. Right click on this path layer and click on 'Stroke Path'