Prep the trim either with paint or varathane to seal.
Sand the trim and apply a second coat of sealer if needed.
Use painters tape to map out the design on the floor.
Measure each length of tape and cut each piece of trim to length.
Make sure to use a level to get the first horizontal piece just right.
Use a stud finder to find the studs and use a finish nailer to nail the trim into them.
Continue with each section of trim, about 1” apart.
Fill the nail holes with wood filler.
Coat with varathane to seal.