Short code doesn't work

I am a website administrator coming to WordPress from a Dreamweaver background. Our company’s website has a custom theme, but the developer says it should work with all plugins.

Soliloquy is the first plugin I personally added. I have been able to set up the slider, but the pages do not recognize the shortcode even when using the Soliloquy button. I had a similar issue when using the native Gallery plugin even when inserted using Insert Media button.

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This may have to do with the entry box editor being revised to allow me to work in HTML or VISUAL.

I have been told on a board that I may need to add code to the functions PHP panel that would make the site recognize shortcode properly — but I have not found where to add the suggested code that is below.

add_filter(‘widget_text’, ‘do_shortcode’);

Is this code right? And, if so, where can I place this code?