If your application is accepted and you have indicated when you want the cover to start, the policy will have been set up taking your wishes into account and send you your policy documents. If you have not indicated when you want the cover to start you will be contacted and the policy documents will be issued in due course.
Policy documents will be posted to you.  They include a policy schedule which contains the specific details of your cover (type and amount of cover, term of cover etc) and the policy conditions which set out the policy terms and conditions (e.g., definitions of terms, when the cover is payable etc.). You should keep the policy documents in a safe place for future reference.