I want to implement integrating 2 salesforce orgs.I followed below Q&A from stackexchange.I have written apex class also.I am not sure how to call this rest apex class.Do i need to add any custom button for this.
Few months back, I've written in detail(step by step) to connect 2 salesforce orgs using Rest API
Please go through it and revert in case of any questions.
You can call that class through trigger with specific values.
If you need more clarity on this tell me what purpose you implemented the class and post this class here.