Using sessions in Akelos is as simple as simple as using PHP $_SESSION

If you want to use store sessions on the database you need a sessions table. You might already have such table it if you used the web installer otherwise you can use this migration

class DatabaseSessionsInstaller extends AkInstaller
{
    function up_1()
    {                
        $this->createTable('sessions', '
        id string(32) not null primary key,
        expire datetime,
        value text'
        , array('timestamp'=>false));
    }

    function down_1()
    {
        $this->dropTable('sessions');
    }
}

once you have a sessions table you need to tell Akelos you want to use the database session handler by defining in your config/config.php

define('AK_SESSION_HANDLER', 1);