You can indicate that a reply to a topic is the solution by clicking on the Solved icon 
on the post’s toolbar.
The toolbar itself is collapsed by default but will be expanded when you click on the ellipsis icon 
next to the Reply button for the specific post.
When a topic is solved the following actions occur;
- the topic will be set to auto-close after a period of time
- a short summary of the solution which links to the specific post is included in the initial post
- a solved icon will precede the topic’s title on the various topic views, indicating to everyone it has been solved
Note:
- only one reply can be used to mark the topic as solved
- only the original author of the topic can mark the topic as solved (with the exception of moderators/admins)
- if you find the answer yourself, please create a reply to your post, provide the solution, and then mark your reply as the post which solves the topic
Please do not add prefixes or suffixes to your topic title, such as [Solved] or (Solved), these reduce the readability of the topic title itself and are unnecessary.