Hi ErnestV,
As far as the REST API is concerned, TKB nodes are just another "Board", so you can use any of the same methods you would for any other "Board":
http://lithosphere.lithium.com/t5/rest-api/bd-p/developers-rest-api?branch=Board
Let's use the Developers Knowledge Base as an example:
http://lithosphere.lithium.com/t5/developers-knowledge-base/tkb-p/studio%40tkb
The id for this TKB is "studio@tkb". If you URL encode that id, you get "studio%40tkb". So this encoded ID is what you'll want to use for your calls.
For example, you can get an individual TKB if you know the id:
http://lithosphere.lithium.com/restapi/vc/boards/id/studio%40tkb
You can also get recent TKB artcles
http://lithosphere.lithium.com/restapi/vc/boards/id/studio%40tkb/threads
There are many other methods available for "Board" objects, so be sure to check out the first link I added.
You can even request a list of all the TKB nodes in the community:
http://lithosphere.lithium.com/t5/rest-api/bd-p/developers-rest-api?leaf-id=Community.nodes.type.key.node_type_key#Community.nodes.type.key.node_type_key.nested
For example:
http://lithosphere.lithium.com/restapi/vc/nodes/type/key/tkb/nested
I hope this helps! If there's something specific you're trying to do but are having trouble figuring out, let us know and we can try to point you in the right direction.