# Use Signed Transaction

## [Buy API (Postman)](https://www.postman.com/tronsave/workspace/tronsave/folder/29749953-d79c9a0d-9ca8-4933-9c1e-d4b8d19effa6)

## Buy Energy with Signed Transaction Flow

### **Step 1: Prepare Wallet and Private Key**

1. Ensure you have access to the wallet's private key you intend to use for the transaction.
2. Verify that the wallet has sufficient TRX balance to execute the transaction.

### **Step 2: Estimate TRX Required**

* The [Estimate of TRX](/developer/rest-api-v0/buy-on-rest-api/use-signed-transaction/estimate-trx.md) API will be used to calculate the TRX needed for the desired energy amount and rental duration.

### **Step 3: Generate a Signed Transaction**

1. **Option 1:**[ **Write your function**](/developer/rest-api-v0/buy-on-rest-api/use-signed-transaction/get-signed-transaction.md#option-1-write-your-function-get-signed-transaction) to generate the signed transaction using the wallet's private key.
2. **Option 2:** Use Tronsave [Get Signed Transaction](/developer/rest-api-v0/buy-on-rest-api/use-signed-transaction/get-signed-transaction.md#option-2-use-tronsave-get-signed-transaction-api) API to generate the signed transaction automatically.

### **Step 4: Create an Order**

* Use the [Create Order](/developer/rest-api-v0/buy-on-rest-api/use-signed-transaction/create-order.md) API to finalize the transaction.
  * Pass the response from the signed transaction (if using the API) or your custom-signed transaction.
  * Include the estimated TRX amount and other required parameters to create the energy purchase order.

## API List for Testing - TRON Nile Testnet

{% tabs %}
{% tab title="Test\_API" %}

* Estimate TRX: <mark style="color:orange;">`POST`</mark> `https://api-dev.tronsave.io/v0/estimate-trx`
* Get Signed Transaction: <mark style="color:orange;">`POST`</mark> `https://api-dev.tronsave.io/v0/signed-tx`
* Create order: <mark style="color:orange;">`POST`</mark>  `https://api-dev.tronsave.io/v0/buy-energy`
  {% endtab %}
  {% endtabs %}


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