# How to purchase using Arbiscan

{% hint style="warning" %}
**This sale is now archived — Checker Node Sales closed in March 2024.**
{% endhint %}

## Prerequisites

* Ethereum-compatible wallet (e.g., MetaMask)
* Sufficient balance of the payment token and some ETH for gas fees

## Step 1: Approve IFFixedSale to Spend the Purchase Amount

1. **Find the Payment Token Contract:**
   * Go to [Arbiscan](https://arbiscan.io/) and use the search bar to find your payment token contract. You will need the contract address of the token you intend to use for the purchase.
2. **Interact with the Contract:**

   * On the token's contract page on Arbiscan, navigate to the `Contract` tab and click on `Write as Proxy` or `Write Contract` if it is not a proxy contract.

   <figure><img src="/files/TZHodieVbu573zkz3FNr" alt=""><figcaption></figcaption></figure>

   * Connect your wallet by clicking on the "Connect to Web3" button. This action will prompt your wallet to ask for permission.
3. **Approve Spending:**
   * Find the `approve` function in the list of available functions. You'll need to input two pieces of information:

     <figure><img src="/files/GbYpftZCP2ZRI3oa5Kgk" alt=""><figcaption></figcaption></figure>

     * The `spender` address, which is the IFFixedSale contract address. This address should be provided by the project.
     * The `amount` of tokens you wish to allow IFFixedSale to spend on your behalf. This will be your purchase amount.
     * After filling in the details, click "Write" to execute the transaction. Confirm the transaction in your wallet and wait for it to be confirmed on the blockchain.

> 💡 The amount is in wei. Use this tool to convert the amount into wei: <https://arbiscan.io/unitconverter?wei=0>
>
> e.g. If the sale is 10 WETH and you’d like to buy 3 sale tokens / nodes. The amount will be 30 ETH(1), which is `30000000000000000000` Wei(10^-18)
>
> ![](/files/O1dVVKb9dYhUcyh0rG6Z)

## Step 2: Purchase Token Using `whitelistedPurchaseWithCode` Function

1. **Navigate to IFFixedSale Contract:**
   * Similar to the first step, search for the IFFixedSale contract on Arbiscan and go to the `Contract` -> `Write Contract` section.
2. **Connect Your Wallet:**
   * Connect your wallet if you haven't done so already by clicking the "Connect to Web3" button.
3. **Execute the Purchase:**
   * Find the `whitelistedPurchaseWithCode` function. Input the required parameters as follows:
     * `paymentAmount`: The amount of tokens you want to purchase. Should be same as the amount approved in step 1
     * `merkleProof`: An empty array.
     * `_allocation`: Set this to the same value as your `paymentAmount`.
     * `code`: Input the referral code provided to you, if any.
   * After entering all the required information, click "Write" to execute the purchase. Confirm the transaction in your wallet.


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