Once After Effects is restarted, you should find the Glitchify plugin in the effects menu. Apply it to a layer, and experiment with the controls to achieve the glitch effect you're looking for.
This is the "poor man's Glitchify." It works for 90% of projects. glitchify plugin after effects download
Once you have downloaded the plugin or script, follow these steps to get it into After Effects. Once After Effects is restarted, you should find