Oauth resolution implementation for CORS error

In our team we are integrating Confluence with our internal application. The integration was done but while dev deployment, we received CORS error. To resolve the issue we worked on Oauth resolution as mentioned in below link https://developer.atlassian.com/cloud/jira/platform/oauth-2-3lo-apps/
We want to know how we can integrate this in our application.

Welcome to the Atlassian developer community @Confluenceipmsuser,

I’d like to help but CORS + OAuth 2 (3LO) isn’t enough context for me to understand your problem. Could you have a look at the following and post some additional details?