How do I create a new segment in the lead database?

In the Lead Database, Right click on the folder called "Segmentation" and create a 'new segmentation'. You can then choose the various segments you want to include. For example, we have a segmentation for record types called "record types" and we have a Channel, SMB, Enterprise, etc segment. Once that is complete, you can click into each segment and edit the criteria with the associated smart list. 

To approve the draft, just right click on the segmenation group name and click approve. It can take a long time for the approval to happen depending on how many records you have. I've heard of it taking up to 24 hours.

Please see my documentation:

http://www.marketingrockstarguides.com/how-to-create-marketo-segmentations-1371/