When using a flat wall solar panel for the first time, is it better to add medium or water first?

Hello, for the first time you use the flat panel wall mounted solar panel, you need to connect the inlet and outlet pipes first, add water, then add antifreeze (if you do not add water, it will easily dry out and damage the parts inside). Pay attention to how tight they are. Anti-leakage seal, it is recommended to check the antifreeze level from time to time through the observation hole, and add it in time once the fluid is found to be insufficient. .