Osama,
If you downloaded Stealthwatch version 6.10 from Cisco dot com then you do not need a trail license. Version 6.10 and later features a 90 day trail license included with the product download.
By the way, you will also need a Flow Collector.
Hope this helps.
Brian
Brian Ford | brford@cisco.com | brford@yahoo.com | 51 75 61 6c 69 74 79 20 6d 65 61 6e 73 20 64 6f 69 6e 67 20 69 74 20 72 69 67 68 74 20 77 68 65 6e 20 6e 6f 20 6f 6e 65 20 69 73 20 6c 6f 6f 6b 69 6e 67 2e | Email me when you figure this out.