How can I enable multiple tag filtering in the Warehouse theme?

[JamesB2000]

I purchased the Warehouse theme recently and I'm looking to put it live on my website soon, but one issue I still have is with the collection filters.

I want to have the collection filters in a way where you can select multiple tags at once, e.g: filtering by "apple" and "kiwi" flavours, but when I try to click on the second tag, it unfilters from the first one, so only shows "kiwi" flavours.

Is there a way to do this? I was told it could be done with Javascript but Im unsure how to put that in.