If you don't have Math Wallet, feel free use its web application or download the app:
Once Math Wallet is prepared, open the app and Create/Import an account.
For Importing an account, you can use the mnemonic phrase/seed or restore JSON from another app/mobile wallet.
For Creating an account, please keep the mnemonic phrase/seed of your account carefully. You can choose to either transfer KSMs from your old address, or purchasing KSMs from Math Wallet's Buy/Sell section with fiat, or withdraw KSMs from centralized exchanges to your address.
Click on "Auction"(it is actually for the crowdloan) on the sidebar and select Shiden Network.
Enter the amount of KSMs that you hope to contribute, carefully review and confirm.