Gravity model using Paneldata from CEPii

Hi,

This is my first time using STATA and I have a hard time getting the hang of if. I want to preform a gravity model using panel data from CEPII website.
My data is generated like this:
Array

What I am wondering is following: How to I organize my data so I can tell STATA it is panel data so I can add fixed effects for time, export and import? I want iso_o to be the panelvar and Year as time. Also how can I test for heteroskedasticity?

Thank you in advance.

Kind regards,
two incompetent bachelor students