I’m not sure I’m following? This is the topic for the Solved plugin, which is the the one that allows the ability to accept solutions on topics. The link in your previous post (https://meta.discourse.org/t/install-plugins-in-discourse/19157) is the general instructions on how to install plugins.
If you have a specific question about a plugin, the best place to ask is either on that plugin’s topic, or (if it’s an official one) in a support topic with the plugin’s tag (eg solved) 
But to answer the question 
, you can currently only have one answer accepted as a solution for each topic.