how can i vote others post?

Am quite new to this site and I understand the voting stuff. Thanks.

You can go to the IndiVine page, where you can find a list of posts that are submitted by various bloggers. 

Once you click on the link or click the button "View post to promote", the button changes to "Promote this post" automatically. The blog post link opens in a new window. 

Once you have read the blog post, you can come back to the same IndiVine page and click on the "Promote this post" button and you have registered your vote for the bloggers post!