You can upload video and audio in user’s activity and add add video and audio or file as attachment.
Registering for becoming a member is free.
There are two packages which are VIP Membership and Premium Membership which is above free level and allow access to more features. For a detailed info about them please register and go to levels in community tab in Menu or Click here
Making your profile private will allow only your friends to view it.
You can do it by going to Account Settings> Account Privacy> Private Account
For adding a post for main page you need to have Premium membership level after which you can go to my posts in menu and Write post where you can write post.
You can only edit the post added by you.
For this go to My Posts> Post Dashboard
Here you can Edit / Delete your post.