Add and remove taxonomies: Add tags
To add a new tag you will need to perform the following:
    - Use 
TaxonomyManager which is the manager class for taxonomies.
     
    - Get the 
Tags taxonomy object.
     
    - Create a new taxon of type 
FlatTaxon.
     
    - Assign the 
Tags taxonomy to the taxon item that you created.
     
    - Add the taxon to the 
Tags taxonomy.
     
    - Call the manager’s 
SaveChanges method to persist the changes to the database. 
Use the following code sample: