The Euskotren (Bilbao - San Sebastian - Hendaye) are still not reflected in most planners.
Eurail is not valid on their services. Tickets cost a few €, available at ticket machines there. The network works like a big subway system. :)
Timetables are available on https://www.euskotren.eus/en and on Google Maps.
Since the pass is only useful for the Bordeaux-Hendaye leg, it might not make sense to use a pass day.
Euskotren timetables are uploaded to MERITS (European Timetable Centre), so they're actually in a lot of planners, but Euskotren publish timetables max. 1 month in advance. Currently in the DB planner until 20/1.
Break it down into smaller chunks, and it will be easier to find the trains. Also, unless you need to go straight to Bilbao, it makes sense to visit San Sebastián first.
Bordeaux - Hendaye - 2.5 hours by TGV (reservation needed) or TER (no reservation needed)
As @thibcabe says, your pass isn’t valid on the Euskotren - buy tickets locally.
Hendaye - San Sebastian-Donostia (Amara) - 40 minutes by Euskotren
San Sebastian-Donostia (Amara) - Bilbao - 2.5 hours by Euskotren
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Note that Hendaye is Hendaia in Spanish. San Sebastián is Donostia in Basque, and Amara is the most central Euskotren station in San Sebastián-Donostia! (Though other Euskotren stations might be closer to your accommodation).
Same in Bilbao: there are several Euskotren stations, so pick the one closest to your accommodation.
