You can find our Wordpress Plugin under "Yumpu ePaper publishing" or here: https://wordpress.org/plugins/yumpu-epaper-publishing/
For the usage of the plugin you need the API token of your account. Here's how you find the token
Download and activate the plugin in WordPress (in the Plugins menu)
Go to “Settings” –> “Yumpu PDF Settings”
Insert your Yumpu API Token (read here how to get it: http://support.yumpu.com/en/question/yumpucom-developer-interface)
Go to the menu point “E-Paper”, upload your PDF’s and insert the generated shortcodes into your posts or pages