Instructions for purchasing coins on decentralized platforms (using Uniswap as an example):

1. Wallet setup: First, you need a wallet compatible with Ethereum, such as MetaMask. Install the MetaMask extension in your browser and create a wallet.

2. Buying Ethereum: Since most transactions on Uniswap are conducted using Ethereum, you need to buy Ethereum first through a centralized exchange or other services and transfer it to your MetaMask wallet.

3. Going to Uniswap: Visit the Uniswap website and connect your wallet using the "Connect Wallet" button.

4. Exchanging for another cryptocurrency: Select Ethereum as the source currency and the cryptocurrency you want to buy as the target currency. Enter the amount of Ethereum you wish to exchange and confirm the transaction. Uniswap will automatically process the exchange, and the new cryptocurrency will appear in your wallet.