E-Commerce Shipping

I will be the first to tell you i’m way out of my league. We started this business last year and it’s going very well but I have absolutely NO experience building or working with websites. Everything i’ve done so far has been trial and error. But this is MUCH more involved than I could have imagined.

I have absolutely no idea how to connect my USPS shipping option to the USPS servers. I got an email from USPS upon registering for their web tools with a list of stuff I need to do, and all in words I don’t understand. Things like “xml string” and “API”. So i’m kind of looking for a step by step guide for this, and I can’t find it on google or anything. Anyone know where I can find that, or wants to help me? Thanks!