Are Paying Quarterly Estimates Really That Simple?

So, I just started freelancing. I know I have to make quarterly estimates for both federal and state income. However, I looked at the process and... is it really that simple? Just go online, calculate what I owe, and pay?

I ask because I looked at the paper options for paying quarterly estimates for both federal and state. In both cases, there's like nothing there but instructions, a worksheet which we are told NOT to send in, and payment vouchers. Would a person paying quarterly estimates via snail mail really just send in those tiny vouchers and a check or money order? They wouldn't even have to send in a worksheet? I feel like it's more complicated than that. Taxes are always more complicated than first meets the eye. I just wanted to make sure I'm not missing anything before I start paying quarterly estimates. Thank you!