After searching for the gene, and clicking through the results, you should see the OSM gene tab shown below.
The gene tab for human OSM is shown in the figure above.
Three protein-coding splice variants are shown in the transcript table [A], each with a unique ENST ID. They are also shown in the image [B] below the table.
How do you choose a transcript? This will depend on which splice variant you are interested in. If you're not sure, the transcript with the CCDS ID is a good start, as the coding sequence is agreed on between several projects.
To choose the CCDS transcript, click on ENST00000215781 [A].