The instructions apply to the Instagram app for iOS and Android.
Kapwing will put a watermark on the bottom right side of the photo.
You could instead use aphoto editing toolif you’d rather the watermark not be displayed.

Tap thearrownext to Create new, then chooseUpload.
TapClick to Upload, and then pick the photo you want to resize.
pick the imageyou just uploaded to load it into the editor.

TapProjectfrom the options at the bottom.
SelectHorizontalto bring up the menu, and then pickInstagram Post Portrait (4:5).
The border will be blurred automatically; to pick a color instead, chooseColorand then select one.

TapResize Projectso that the photo conforms to the Instagram post size rule.
Kapwing also lets you remove the background.
Tap the photo and chooseAI Tools>Erase.

Also feel free to use any of Kapwing’s other tools before finishing up.
TapExportwhen you’re ready to save the image.
TapExport as JPEG>Download.

you might now post the new photo on Instagram.
FAQ
Because all Instagram posts are 4:5, landscape and portrait images will always have a border.
However, you’re able to choose a background color other than white with the Kapwing website.