At the bottom of the Entity Index (aka the 'EI') you will see the search control, consisting of:
A text box (where you input the value to be searched)
An 'X' button (quick way to clear the text box)
A 'Search' button (executes your search), and
A drop-down arrow button (contains the search options)
To search, enter a word or words that you would like to use as a search
Hit <Enter>
Note the number of hits, e.g., 4 hits
Headings for records that match your search will be highlighted, but you may have to go up and down the page to see them all
To change the search options, click the drop-down arrow (as in the above screenshot).
Search Composite key only: limit the search to the 'Composite Key' column of the EI
Search Identifiers only: limit the search to LCCNs, ISBNs, and other entity Identifiers
Search relationships only: limit the search to RDA relationships
Search CK + Identifiers (default): search the 'Composite Key' column of the EI and also search LCCNs, ISBNs, and other entity Identifiers
Search Element name or Id: assumes that the text to be searched is
a RIMMF Element Id (5 digits)
an RDA opaque element Id ('P' + 5 digits)
an RDA lexical element name in English
Search Whole Record: searches the entire contents of all records, with the following caveats: