How to: Lookup multiple tables InventTable and PurchTable

I have to create lookup from 2 datasource.

I find this tutiorial: https://community.dynamics.com/ax/b/daxbeginners/archive/2014/05/20/how-to-create-form-lookup-lookup-multiple-tables.aspx

but I don't know how to do it.

1. In the AOT, create a query.

2. Drag and drop InventTable into Data Sources. Set the Fields properties Dynamic toNo.
Now, drag and drop the fields ItemId and NameAlias and Product to Fields.

3. Now, it’s time to create the relationship between InventTable and PurchTable [I don't know how?]

when I create View I ony one datasource

Next I have to create lookup form in fields: 

(InventTable,ItemId)

(InventTable,defaultProductName)

(InventTable,itemGroupId)

(InventTable,NameAlias)

(InventTable,Product)

(PurchTable ,PurchaseType)

What can I do, when next to i View i see only one datasouses InventTable_1, why i don't see PurchTable_1?

thank you very much to help.