Hello Navid,
You need to select the right footprint when you create the part. Since the part is already created, this article will guide on how to change it.
For future reference, please follow this tutorial while creating custom components. Step 2 is precisely the footprint selection and step 3 the symbol edition. In step 3 you can choose to create a symbol or to copy one from the database, which is usually faster.
Something to consider is that the amplifier symbol s a triangle for the ANSI standard but a rectangle for the IEC. Please see this article and verify the ANSI standard is selected by default. I don't think the setting is set to IEC as all the amplifiers will look like a rectangle, but I still wanted to share the article with you. If the setting is actually wrong, set it to ANSI, click OK and go to Tools > Update Components and click the Update button.
I hope you find the information useful.
Camilo V.
National Instruments
