Close all versions of Firefox

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In windows go to start (or hit Windows Icon + R on the keyboard)
then to run
in the run window type in firefox.exe -p

hit OK
you should then get prompted by profile manager.

(if you have not closed all versions of Firefox you will not see the Profile manager, you will simply enter Firefox.)
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select create profile |.............(you can also use this menu to delete a profile when you wish to)

follow the prompts
create a name of your choice when prompted

select finish

you will then see the names of the profiles that you are running in Firefox.
select the one you want to run and hit start firefox

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So if you want later to change which profile you are in.
Close all Firefoxes

Go back to the run prompt.
What you have typed in previously should still be in the run Window, so no need to retype.
When you are in Profile manager select the profile that you want to use and hit start Firefox.
You will then be in the Profile of your choice.

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Once you are in a particular Profile you can always use your usual Firefox icon to restart Firefox.
You will always remain in the same profile doing that until you change your profile again in the Profile manager.

You can also rename your present profiles following the prompts, to help clarify which is which, and also, but it is good to be careful, delete any profile you wish.

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