Normally...
1. Add flush as per manufacturer's instructions.
2. Run engine to temp and/or time specified.
3. Allow engine to cool.
4. Remove lower hose and drain coolant, remove reservoir cap.
5. Replace lower hose. Refill coolant.
6. Run to temperature with reservoir cap off until all air is expelled.
7. Replace cap, go for a run and check level on your return.
You can also run a normal garden hose in to the radiator after 4 and hose it around. Same from the reservoir cap.
