Sorry didn't see your question. Did you get figured out?

You can delegate staked SPS to Soulkeep through Splinterlands. Go to play..Soulkeep..and instead of "Play Now" look along the top for "Delegate SPS".

How much you need for each league is listed in the Soulkeep whitepaper. Click on the question mark icon in the top left corner of the main Soulkeep page.