Ykhjuy

I am following a wonderful audio to learn the Amidah. It is here on Chabad.

I come from an almost non-religious Jewish family and don't really know which prayers to do and so I am following this. However I cannot figure out what to do on evening Shabbat. I know that the middle is left out but I am not sure what defines the middle in the audio. Can anyone tell me?

Also, is this same version of the Amidah to be used for morning, evening, and afternoon? I read that the Amidah should be done 3 times a day during the week.

Indeed one prays the amida three times a day (four times on Shabbat and holidays), once in the evening (arvit) since the Jewish day goes from evening to evening, once in the morning (shaharit) and once in the afternoon (minha). See here if you are interested in the exact times (definitions are here).

During the week it is nearly the same amida prayer between morning, afternoon and evening but on Shabbat it is a different version. The Shabbat amida has the same first three and last three blessings, but only has one blessing in the middle (making it seven blessings instead of nineteen during the week).

You would need a prayer book (siddur) to properly learn and understand the differences. If you don't yet read Hebrew, you can get a transliterated siddur (e.g., here from artscroll for weekdays, here for Shabbat and holidays). And this appears to be a transliterated online siddur (Friday night here).

There is also a version of the Shabbat amida on Sefaria, here for Friday night, here for Saturday morning.

Of course, nothing beats joining a real Jewish community and asking someone to help you through prayers. Contacting the rabbi in advance is always a good idea so he can pair you up with a friendly congregant. To prepare, take a look at this introduction to the Shabbat service from NJOP, incidentally they run beginner services in many synagogues where thousands have learned to pray.

Good luck on the journey, welcome to Mi Yodeya and don't hesitate to ask here for further questions.