First of all you need to download the Instake Downloader form your Google Playstore then proceed with the following steps.
1. Go over to your Instagram App, find Instagram image or video that you want to save.
NB: Instagram App is different form Instake Downloader
2. Now copy that URL of the Instagram photo or video.
3. Paste the Instagram copied URL in your Instake Downloader and it will download automatically.
Then you’re done