You can't. You have to record in a less reverberant space, or use something like the Universal Acoustics Vocal Screen Lite. The don't cost much, but will improve your situation dramatically at source, and that's always the best way to fix problems like this.

When you record in a reverberant space, that reverberation becomes a part of the microphone's signal. Even if you could get rid of the echo-y part you'd still be left with that, and it would sound very strange. Hence the need to fix the issue at source.