KLM thinks it is enough time, so trust them. I have went through AMS with short connections 2-3 times now, including to Lisbon from the US, and every time I was at the gate well before boarding started.
Your experience will go something like this:
You very well may land early, depending on the jetstream, so possible you gain a little time. Once you get off the plane, you just go out into the international terminal, just follow the signs to "connecting flights".
As you continue to walk down what seem like very long hallways, you will start to see signs for connecting flights, listing specific gates. There is no single immigration point for connecting flights, they break it up into several points, with each serving a section of gates. Just look for the point for your gate, follow the signs, and you will see the line.
At the head of the line will be a monitor and likely an agent, if your flight appears on the monitor, you can move to an expedited line. But even me, with an 1:15 transfer, was not on the monitor. But no worries, the line moves quickly, get your passport scanned and stamped and on your way to your gate.
It is possible you may encounter one of the newer e-gates, may be quicker, people may be confused by what to do, but it is easy, place your passport on the scanner, look at the camera, later they will add finger scans. Right now, with the e-gates they are then still stamping your passport as a second step.