Individuals in SalesSeek are comprised of all your contacts. Leads are individuals that have been assigned a Lead Source. If you don't know the correct Lead Source you can still mark and Individual as a Lead by choosing the Lead Source 'Unspecified'.
If you remove the Lead Source from a lead it will still remain as an individual.
Leads appear on most Dashboards with the most recently created at the top. They also appear in the leads section of the app.