Upon opening the browser the first window you will be presented with is the actual HL7 browsing component. It holds HL7 records in a hierarchical tree widget that is a natural expression of HL7's hierarchical structure. You can expand records into segments, expand segments into fields, and expand fields into their repetitions, components and subcomponents.
Opening a file (or reading one from the command line, see input for details) can happen very quickly or take a long time (and a lot of memory!) depending upon the size of the source file and the size of the data in the source file. In one example, a set of almost 3000 records required over 60MB of memory to open, but could do so in about 8 seconds on a fairly typical computer.
During the time the records are loading you will not see any on the display screen. This is done to minimize loading time in the most typical situations. When the load has completed, the records will automatically display and then you will know it is complete. (A progress bar would be virtually impossible to implement in this case because it has no way of knowing how much data that will be piped into the program, for example.)
With the data loaded you should see a list of records in your window. You get more detail from a given record by clicking on it. That will cause the underlying parsing engine to break the record into segments and render those segments as sub-nodes underneath the entry for the record in the window. You can subsequently click on and expand those segments into their constituent components.
Nodes can be edited by right-clicking (or Apple-clicking) on them. When you click OK to finish editing that record will be rebuilt from scratch to ensure your changes are retained properly. Only HL7 V2 nodes can be edited in the current version - V3 nodes are read-only.
You can search within records from the main browser window by clicking on the magnifying glass icon. It performs regular expression searches either forwards or backwards, and by default will search forwards if you just hit enter. There is currently one limitation to searching - only the first instance of the match in the record is displayed.