I have a 1991 honda civic 4 door dx when I turn the key ahead to the on position there is no power when I turn it to start the horn will sound and it will make one click

* Remove and fully charge/replace the battery. Most auto parts stores will test/charge batteries for free.

* Test all under hood and under dash fuses with a test light or multimeter:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-3.html#post252145

* Check the ignition switch for wear, pitting, or melting:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-2.html#post224652

Most likely, the battery is dead.

My batt is good my headlights work and my heater and 4 way flashers but still noting on the key

Heatlights, heater, and flashers working does not, by a long sight, prove that the battery is good. Starter motors draw much more amperage than those items.

Read this link:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-3.html#post235560