If you're new to Splinterlands it's quite complex.
SPT is a side-token of Hive (there are many, LEO for example is another) - it only has one point of issuance which is the case with all of these tokens, so they are not truly decentralised.
Having said that, this hasn't stopped me from accumulating almost 1M SPT (I'm a big believer in Hive and its communities)
SplinterTalk.io is basically a clone of the Hive front end, but if you use the SPT tag anything you post on Hive is also rewarded in SPT.
You can post via Hive, or via the splintertalk front end (the later is a bit clunkier) and still earn both HIVE AND SPT.
You can buy SPT on Hive-Engine - https://hive-engine.com/
To stake it you need to go to your wallet which you can do by accessing Splintertalk - https://www.splintertalk.io/ - click on the wallet link (you can also stake via hive-engine).
As someone else said in the comments - you can just earn by posting decent splinterlands content on any of the Hive front-ends and using the 'spt' tag when you post.
Like most Hive side-chain tokens, you earn 50% of your curation rewards for upvoting, but you need spt staked to earn!
I'll be happy to answer any questions - just drop them in here, NB I don't check this alt account much for replies so may be a day or two getting back to youl.
OH, if you buy and hold spt (you don't have to stake you earn SPS rewards - it qualifies for the drop. Check the SPS whitepaper for the rate.
Wow thank you for that very informative response. This totally helps me out a lot more! I was wondering since I staked my 6 spt how do i upvote with spt on other people's comments?