You can use this form to create a new Purchase Order to register a planned purchase. First, select Order for Purchase as the transaction type – this will make available the appropriate fields.
On the Main tab, the following fields are required: Company, Contract, Delivery Date, and Entity.
The "Purchase Order (create)" form. The Main tab
<Auto> in the Number field indicates that an internal number for this document is assigned automatically when you save the document. The From field is populated automatically with the current business date. You can select another date, if necessary.
In the Entity field, select an entity of your company which is responsible for the document. The Entity field is available if the Multi-Company Accounting option is selected on: Administration > Settings > General Settings. You can select your personal default entity to appear in documents; for this, refer to Personal Settings. If you have not selected your default entity, the entity defined first will be used as the system default value.
In the Company field, you can select an individual or a legal entity from whom You you want to purchase some goods or services.
The Contract field is populated automatically with the default contract of the selected company. If necessary, you can select another one.
The Customer Order field is populated automatically with the customer order if this purchase order is based on it. To populate the purchase order with the data from the customer order, click the Fill ( 
) button.
The Basis field is filled populated automatically, if the purchase order is based on a document of the following types: Production Order or Quotation. It may be populated automatically if the order is based on any of these documents. You You can manually select the basis document from the list (for this, click Show all from the drop-down list).
You can link this order with a project from the Projects list if the Project Costing functionality is turned on the Administration > Settings > Project Costing. If the items in this document are being purchased for different projects, and you need to specify different projects for different items, you can move the Project field from the Main tab as a column to the table on the Inventory tab. For this, use the Setting button on the toolbar (for more information, see Document Toolbar).
If the Enable Project Tasks option is selected on the Administration > Settings > Project Costing form, you can link the entire document with a specific project task or document's line items with multiple project tasks. By default, the Project Task column is available on the Inventory and Services tabs. If needed, you can move it to the document header (the Main tab). For this, use the Settings button on the toolbar.
...
Notice the hyperlink below the Basis field – USD=3.65AED* WM-Service Limited on the screenshot above (can be different in your document). The currency of the purchase order is determined according to the selected contract. To use other currency in the document, select another contract, or create a new one, if necessary. Click the hyperlink to change the price-related settings for the document. For details, see The Prices and Currency dialog box (Purchasing).
Use the Validate Valid From and To fields if you want to restrict the interval during which this purchase order is valid.
...