You can change, add, or remove your genre or tags from your playlist through the edit page in the Basic Info tab: 

With the genre field you can add the main genre of your track, this will act as the first tag on your track. You have the option to select a genre from the list already included, which are the same as the genres in our charts feature, or enter your own custom genre. 

You can add a tag by typing it into the 'Tags' field. If you have multiple tags but no genre, the first one will be considered your main tag, or genre. This will appear on the Feed and Search pages on your playlist’s waveform.