Before you install a gable soffit, make sure that the roof does not have any repairs that may make the installation more difficult. Be sure to take accurate measurements as well, as this cuts down on errors.
Optimize the airflow by removing existing shingle frieze boards and moldings. Remove any existing rotten fascia for a clean installation, and also remove the gutters in order to avoid obstructions, though you can later reinstall the gutters. To install the fascia trim, begin at the corners, cutting carefully and bending them over to create a form box for the rest of the system.