Well, I had some trouble figuring that our earlier and no help was found through google or youtube or even on discord support.
Had to do some trial and errors for that.
This will be the guide for who have bought SPS through Meta Mask and used Pancakeswap.
FIRST. Make sure you have your meta mask logged in on your Google Chrome.
SECOND. Make sure your Meta Mask is on BSC network.
THIRD. Login into your Splinterlands account and click on your profile name. This will popped up a droplink as per pic and click on link external wallet.
FOURTH. It will popped up a menu such as per pic below. Click on Binance Smart Chain. Then click on your find my address, tick on "I acknowledge...." then click on SAVE.
FIFTH. On top of your Splinterlands there will be Credit, DEC and SPS. Click on SPS.
SIXTH. It will popped this up after you have clicked on the SPS. You will see your balance of SPS that you bought thru Pancakeswap on that Binance Smart Chain. Somehow you do not see it as In-game Balance. You will need to transfer it onto your player's account to make it visible. Click on transfer
SEVENTH. Once you see as per pic below, key in the SPS amount you want to transfer into your player's account. Select the Binance Smart Chain network and click on Transfer In. Then your Meta Mask confirmation will popped up. Approve the gas fees confirmation.(Might need to do twice?)
EIGHTH. You can check the confirmation through your Meta Mask by checking on the activity. (Please ignore the failed part. It popped up twice and might need to do twice for confirmation. >_< ! )
NINTH. Now you will see the SPS balance in game !
TENTH. AND YOU ARE DONE! You can stake all that SPS you bought from Pancakeswap and get your rewards there!
THANK YOU!!!!!!!!!!!!!!!!!!!!!!!!!! OMG I have been struggling with this, I Can't it was so simple I feel stupid now ... You're a life saver.