I had to go into Splinterlands.com and try some experiments ….

You have to create sets to rent out ….

I created 3 sets with different cards and rent them For 1 DEC per card .. the one with 69 cards rented out but so far the other 2 sets did not rent out …. I don’t understand why. I might be renting out for too cheap but getting anything is better than getting nothing ….
Step 1 : click on Items at top

Step 2: : Click Card Sets

Step 3: Click Create and select the cards for each set

Give a name and set a price and wait for someone to rent ….

Woops …. Just checked have now rented out 2 sets