How to consume external API in gadget?

Hi,

I have to create gadget which is nothing but simple html table (refer
screenshot). I have external rest api ready which is giving data required for html table.

I need to know, how to use that API so that I can render data in gadget. I am beginner. please share some sample example or link.

please refer screenshot of gadget. here values - A, B, C, D with count are populated hardcoded on gadget. but now I have API which is giving those data. I just have to use that API but dont know how to use that API in gadget. please help. thanks in advance.