will not let me add effects

In audacity I recorded some audio for a gameplay and now when I go into effects it will not let me use any of the effects. For example I would like to use the noise reduction effect. when I go into effects all but phaser whawha and pc4 are grey and will not let me click on them. Somebody please help.

For most effects, playback needs to be stopped (not just paused). Try clicking the Stop button.

Phaser and whawha are currently the only two built-in effects that have “real time preview”. Some optional plug-in effect also support real time preview. Effects that support real time preview can be opened while Audacity is playing (or paused). (http://manual.audacityteam.org/man/real_time_preview_of_effects.html)