How I can change the ram of my laptop?

you need to provide the laptop series code as lenovo yoga has many variants, or you can post the picture of the bottom case of your laptop, but usually lenovo yoga series ram is not upgradeable.

In general, the Yoga series is a soldered RAM series; there was only one partially soldered exception as a one-time happy accident (the ThinkPad 15" version) but after Lenovo began making the entry-level (read: non-P series) laptops "maintenance contract" machines with soldered RAM and soldered WLAN cards (note: 15/16 "p" is immune to the soldered RAM fail, but has soldered wireless) that machine died :-(. That blunder was well and truly dead when they made the Yoga an X1 Carbon but with a 360-degree hinge and made the switch to soldered prior. It was a one-time blunder, and we lost it :-(.

Seriously... the last survivor before this garbage with Lenovo is the XX80 series, the XX90 series on the lower-end platforms is either fully soldered ("s") or single SODIMM ($$ RAM upgrades, once it dies that's it). Lenovo and Dell are off the "good buy" list for this garbage, as well as anything Intel EVO or HP EVO. HP survived the entry-level bad list because of machines like the G5-present series, and they have begun selling more of the parts for the G7 series. It's almost like HP saw how rough the new Lenovos and Dells are, didn't copy the bad parts, and built a laptop that is well-built, easy to repair AND parts are available.