A Helix Collection window (see the window in the background of the illustration) contains Relations, Sequences, and Users. It is the top-level of a Helix database (known as a Collection).
The Relation contains a table of records along with a set of tools (Abacus, Query, Index, and Post) to work with the records.
To use a new icon, simply click on the appropriate tool in the Icon Well (along the left side of the window) and drag the icon into the Relation window.
To throw away an unreferenced icon, just click and drag the icon into the Trash.