The high point you should use are usually the most recent high. As for the time frame to use, it depends on your trading style. If you are trading off the 15 minutes chart, the high will be at that time frame and if you are trading off the hourly chart, the high will be from that time frame.

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Here Is How You Should Plot Your Fibonacci Levels In An Uptrend

Step 1: Using the tool provided by your platform, Pick a high point and a low point
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so Step 1 : it’s yesterday high point ? or week high ? there are too many high ponts, so how can i pick a high point ?

and which time frame ?

thanks so much