SPLINTER TROUBLE

Hi everyone my name is Chinedu Onyebuchi, I am a Nigerian🇳🇬!.
I'm so excited to be a part of a decentralized community #Hive which I saw on Twitter and I am also new here!
After logging into #peakd I saw splinterlands with I asked @kennethBosak to send a referral link to me which I've been waiting for since Saturday.
Immediately I signed up because I don't know-how #Hive works, starting with something I am familiar with was the best. After I signed up I had trouble playing, I lost two battles already because I was naive.
It seems pretty hard to play compared to Lord Mobile the only online game I play, But I choose splinterlands because it is based on blockchain. I got sick staying at home during the pandemic that took everyone unaware. I found myself in the world of CRYPTOCURRENCY and I'm so interested in it.
So instead of playing a centralized Lord Mobile, I go with promising splinterlands. But first I need your help guys I don't know how to play!

*HOW DO I SELECT THESE CARDS

*HOW DO I REMOVE OR EVEN SWAP THEM

*AND HERE I LOST WITHOUT PLAYING!
THANKS FOR HELPING ME ALREADY.
HAVE A GOOD-NIGHT REST