Open Photoshop and go to file
Click open to import the image you want to edit
Click the "Image" menu.
Select the "Image Size" option.
Locate the "Resolution" field and increase the figure to 300. Click "OK" to confirm.
Increase the size of your image by entering the numerical values in the "Height" and "Width" fields (insert 2 by 2 in both fields).
Save the document by pressing control X (a popup window will appear). You will discover that the height and the width of the image will move to 600 by 600 dimension
In that popup window, change the dimension to 128kb.
Save to your system or laptop
Go to the NNPC webpage.
In the upload passport link, click and upload the image you saved on the page

If you try and it didn’t work,
Open the saved image with paint
Reduce size. Make sure the head of the image is 50-70% of the whole passport.
After the above, don’t do anything just go and
Repeat the same process from the top with Photoshop

Further info: Click the "Resample" checkbox and select "Preserve Details." Use the "Reduce Noise" slider to tweak the sharpness of your enlarged image. Click the "OK" button to confirm your selection.

for information on other tools, you can use to edit, check the link below

https://www.scitechinfo.com.ng/blog/2019/03/20/how-to-edit-and-upload-image-for-nnpc-recruitment-application/