In the Choqok main window there are some timelines allowing you to see what your friends have posted, replies to them and direct messages sent and received from friends. You can also post a new message.
All of this will be available when you configure at least one account in Choqok.
You have one tab per account, on the screenshot you can see a tab with the alias identica and another with the alias twitter.
On top of the tab you can choose to send a direct message to someone who is subscribed to your account. You can send direct messages to other users of the same service, as long as both of you are subscribed to each other. If you leave Direct message to unchecked your message will be posted publicly and all your friends will read it. If you check it, you will then choose a name in the list and the private message will only be posted to this person.
The text area allows you to post your message which must have less than 140 characters. The number of characters left is displayed in green on bottom right under the text area. The color changes to orange when you reach the 30 characters limit then to red when you reach 0. If your message is longer than 140 characters, you will be asked if you want to post it anyway. If you agree, it will be posted up to 140 characters.
The Home tab displays the timeline which consists in all posts you and your friends wrote. A post using Identi.ca is called a dent while a post using Twitter is called a tweet.
The Reply tab displays posts that are replies to you.
All the private messages you sent will be displayed in the Outbox tab while the received ones will be displayed in the Inbox tab.