How do I boot manually from USB?

How do I boot manually from USB?:

Hello

Thanks for the help with using a liveUSB to try Ubuntu!

Now that I have played around with it on my current computer, I am ready to try it out on my old dated computer. Only thing is, I don’t know how… My current computer just boots up to a selection screen when the USB is in there, but my old computer does not. I don’t see a program that let’s me load it from the USB but I’m sure its there. I just need some help from a pro!

submitted by /u/Dipsquat
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