As mentioned below, you can either request your Principal or either of your teachers who teaches you. All that is required is the teacher’s email address and he will receive a request from common app. Things after that are pretty straightforward, the teacher writes a reco and also uploads the profile of the school (if there is no GC, the profile of the school= A one sheet document explaining what type of school it is and where it is located). Please talk to your principal and I am sure he/she will be able to assist. If you do not receive any help, then please let me know and I can do the needful.
If your school does not have a Guidance Counsellor, then your Principal can submit the recommendation and other required materials on your behalf. All you will have to do is go to assign recommenders under the Recommendation and FERPA section of the commonapp and enter your principal’s email (It would be better if he/she has school’s email. For example BNKS’s GC has an email in the format [email protected] It makes it look more genuine) After you assign the recommender, he/she will be invited to make a commonapp counsellor account. After making the account, he/she could then upload the required materials for you. The same thing applies while inviting other subject teachers. See this page from the common app that basically answers your question.