As of IGB version 10.1.0 most of the UCSC Genome Browser genomes and data tracks are available by default in IGB.
Genomes available from UCSC should automatically appear within the Species menu.
When a genome is selected that has UCSC tracks, a UCSC REST folder will appear in the Available Data sub-panel of the Data Access tab. Open the folder and select a track to add it to IGB.
If you do not see genomes or tracks available from UCSC, check the Data Sources tab and make sure that UCSC REST is set to Enabled.