First-off, don't do this on an iPad — they silently block non-modal popups without even asking if you want to allow a required-one.
For an Alexa skill to work, LMS needs to be accessible from the Amazon cloud outside your LAN. This must be a https-secured link and for your own security it should have username/password protection. The free ngrok proxy service is what we recommend for this. You install a single binary on your machine that runs in the background and creates a so-called tunnel between LMS and the cloud. ngrok gives you a convenient personal static domain such as e.g. https://panda-new-kit.ngrok-free.app and they take care of security and SSL certs.
Our form allows you to pre-configure and then download a script that will install ngrok for you and also configure it so that the skills can reach your LMS via that static domain: Alexa ⇆ [443/https] ⇆ ngrok ⇆ [9000/http] ⇆ LMS . The setup process can target pCP, RPi-OS, Linux, macOS and Windows, with a tailored native script for each OS.
You can then complete our form by choosing the OS of the target machine you'll run ngrok on, the LAN IP address of LMS in your local network, and finally choose a username and password to protect the tunnel.
When all that is done press 'Download Script' — your browser may try to block this as a security concern so you may have to deliberately allow the download. The form will first be checked for completion/correctness and if all is ok then account-linking will be unlocked. The button will both install and account-link the skill via an Amazon oauth popup so that you can skip having to use the Alexa app or portal. Note that your tunnel must already be running for this to work as our back-end will ascertain a correct response from LMS before accepting the linking.
During download, a modal showing script-run instructions for your chosen OS will pop up.