How do I search by tags??

You can use this. Or click on a manga, scroll down to where you see the tags on the right part of your screen and click on one tag.

http://www.mangago.zone/tag/

you can either use
http://www.mangago.zone/tag// and imput the tag you want
OR
you can scroll down to any random manwha or manga and there should be a popular tag thing
click it and you should be able to search another one