The answer to 'how to unclog drain trap' is to first try using a plunger or a drain snake to clear the clog. If that doesn't work, you may need to disassemble the drain trap and clear it manually. This involves unscrewing the P-trap under the sink or tub and removing any debris or buildup inside.
It's important to wear rubber gloves and eye protection when working on drains, and to have a bucket or towels ready to catch any water that may spill out. You should also avoid using harsh chemical drain cleaners, as they can damage pipes over time. If you're not comfortable doing this yourself or the clog persists, it's best to call a professional plumber to diagnose and fix the issue.