In the following sentence OK?
"Take Sir Winston churchill for example, a good leader knows how to swim with the tide."
1.Should I use "as an example" instead of " for example"?
2. Should I use a comma "," or a period "." after the word example?
I believe that "for example" is fine, although "as an example" is also correct.
You definitely need something stronger than a comma there. Just about any other punctuation would work: Semi-colon, Colon, Full Stop/Period. Even an exclamation point would work! But not a comma.