My 99 honda civic ex won't start up the car just turns over not slow or bogged down sounding either.. I just installed a after market stereo and since then it won't start I tried unpluging the power supply and still the car won't start.. how can I fix this problem?

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