By default:

- when in EyeTV, pressing and holding the "menu" button will bring up 
the Remote Buddy menu.

- when using a directly supported app, a short press of the "menu" 
button will bring up the Remote Buddy menu.

Please have a look at the dedicated "EyeTV receivers" page to find out 
which key on your remote is the "menu" button. For silver remotes with 
EyeTV label, this is the button labeled "Enter".

Other than that, the only other reason why it wouldn't work would be 
that you are using a - as of yet - unsupported receiver:

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All TV products from Elgato are supported in conjunction with their 
bundled remote control (currently still except products of the EyeTV 
lines 250, 250 Plus, 300/310, 400/410, 500, 610) as well as TV sticks 
by TerraTec and Pinnacle shipping with EyeTV. 
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Please provide me with more details on your hardware setup if this 
does not already answer your question.

Best regards, 
Felix