You can access SPS from Keychain mobile App although its tricky.
Splinterlands.com is not tailored for mobile, m.splinterlands.io is.
But on m.splinterlands.io, there is no SPS page. The solution is to directly paste this url into Keychain : https://splinterlands.com/?p=sps_management

You still have to use m.splinterlands.io to play though.
I hope they will add SPS management to the mobile version soon =) Hope this helps in the meantime