Routine data entry is through a user-customizable collection-specific form. Usage of the form is at least mostly self-evident.
In order to use the form, you need to have the data-entry role and access to the particular collection with which you are working. Also, the specimens for which you intend to enter data must have a valid accession number.
Access to the form is from the Enter Data dropdown in Arctos, or if you are already logged in, from here.
Cross-collection accessions are described under Accession Documentation.
Taxon name functionality is described in bulkloader documentation.