Hey buddy you are getting it all wrong - its not that hard!
First of all see the text at the bottom of your image (just below the sixth point and at the right of "40") - it says:
"Six additional ways of arranging the letters of your message simply"
Think for a moment - re-read that line - these are 6 ways of writing your message (ICANREADTHISMESSAGE) - they are NOT the steps! This is NOT a procedure. What this means is that all these 6 points are INDEPENDENT of each other!
Don't worry I'll "walk" you through them (as you have asked 😝)
I hope first three are clear to you - if you still have some doubt - you can ask me and I'll help you out.
Ok lets see the rest of them:
First the fourth one:
"Write every second letter leaving out those in between; then continue using the omitted letters."
This means that we have to write the alternative letters leaving those in between, following this pattern:
Write Skip Write Skip Write Skip...
and when we reach the end of our message string - use the omitted letters.
So our message is: ICANREADTHISMESSAGE
ICANREADTHISMESSAGE
I A R A T I M S A E
and it says to use the omitted letters, so we continue:
ICANREADTHISMESSAGE
C N E D H S E S G
So finally we get:
I A R A T I M S A E C N E D H S E S G
OR
IARA.TIMS.AECN.EDHS.ESG
Now lets move on to the fifth:
Write out pairs of letters and reverse them; join them to the next two.
So lets first do the pairing part:
ICANREADTHISMESSAGE
IC AN RE AD TH IS ME SS AG E
Now reverse them:
CI NA ER DA HT SI EM SS GA E
Now "join them to the next two":
CINA ERDA HTSI EMSS GAE
OR
CINA.ERDA.HTSI.EMSS.GAE
Now lets move onto the last one, that is the sixth:
Write every second letter with a gap between them; then work back through, placing the missing letters in gaps.
So first let us "write every second letter with a gap between them":
ICANREADTHISMESSAGE
I A R A T I M S A E
Now, we have to "work back through, placing the missing letters in gaps":
ICANREADTHISMESSAGE
I A R A T I M S A E
start from the back - G comes first then comes S - then E and so on"
IGASREASTHIDMESNACE
Notice one thing - they forgot to put a "C" in the second last positions - its a misprint! They don't have it anywhere in their sixth sentence!
I hope this is clear now - if you have any doubt feel free to ask - i'll clarify it 😅