How do you put a curtain in your window in the shower?

I use a tension rod and I cut a clear vinyl shower curtain to size and put in front of a pretty curtain

An expandable shower curtain rod?. I really don't know. I do know that it is a pain to deal with. Google it. Good luck.

Have you considered alternatives to curtains for privacy that still lets the light in? This just one example

https://www.amazon.com/Rabbitgoo-Decorative-Privacy-Non-Adhesive-Control/dp/B019Q2KQ7E/ref=sr_1_21_sspa?ie=UTF8&qid=1537503663&sr=8-21-spons&keywords=window+film+decorative&psc=1

If you search Google for" decorative window film" you will see thousands of different patterns to choose from, and they are so easy to apply using a spray bottle and a credit card. Inexpensive and really pretty. Best wishes.

I used a tension rod and put up a full length shower curtain that matched the other side of the shower.

Tension rod with curtain. I am tall and not an issue for me.

I put a blind on mine, works great

I have used a small tension rod before and it worked pretty good

Try to hang inside the niche the window is in. Stays clean longer.