On tam piše, že ji mám nastravit jako static a pak ji změnít.

1) Connect the laptop to your network and get an IP from DHCP as usual.
2) Go into the Mikrotik's IP > DHCP-Server menu and click on the leases display.
3) Scroll through the leases and find your laptop's lease and double-click it
4) In the window that opens, there is a button on the right hand side "make static"
5) Click that button and you're done.

Once the static lease exists, you can edit it and change the IP address that gets assigned if you want a specific address.