pls i need help

No, you do not need to buy anything to use Mecabricks. To get started, click the "Workshop" link at the top of the screen to take you to the building area. You can then choose what elements to use at the bottom of the screen. Click the "Help" menu at the top for more information on how to get started.

Here is a forum post describing how the building process works to get you alittle help!

http://www.mecabricks.com/en/forum/topic/65

And here is a video showing you how to fit parts to each other using snap points. https://www.youtube.com/watch?v=AsDczg1pOFc

There are also other explaining videos from Mecabricks. https://www.youtube.com/user/Mecabricks/videos