Hi Peggy,
If your sense is that the cat has blocked sinuses and severe congestion, then the upper respiratory formulas will work. Try twice daily dosing of 3 to 5 pellets at a time. You can crush them or give them whole.
If you sense the cat's problem is more serous discharge plus immune deficiency, then the formula Yu Ping Feng San (Jade Wind Screen Powder) is called for. It contains a lot of Astragalus, which stimulates a much more effective immune response. This would seem to be particularly appropriate in herpes virus, where the virus arises directly because of an immune suppressive state.
If you're using the power, go with maybe 1/8th of a tsp BID. You might be able to go with 1/16th tsp BID. It's pretty mild tasting, so putting it in the food will probably work.
Good luck,
Steve