how can i update my phone so i can download instagram
is it updates already
iPhone 6s Plus
The current version of Instagram requires iOS 13.4 or later. If you have an iPhone 6S as suggested by your tag line, then it can update to iOS 15.7.5 ands as such can download and run Instagram without any issue.
If you have an iPhone 6 (no S), then it cannot update beyond iOS 12.5.7 and as such cannot run the current version of Instagram.
If you have downloaded the app previously, you may be able to get a compatible version from your purchase history. Click here ➡️ Redownload apps and games from Apple - Apple Support
If you have never downloaded it before, then there no way to get it now on an iPhone 6.