how to get the play resume after pasting a position?

[evergreen1]

using winboard 4.7.2.I was watching a game of pgn. on the 18th move i have got a thought of a variation. i have pasted the position from to winboard. now i want to test a variation of myself. i make a move of black. Now i made a selection in winboard >machine white. but the machine is not playing. why? does it mean that after pasting a position i have to make both the black's and white's moves to go further.

[H.G.Muller]

Normally this should work. Which engine did you have loaded?

[evergreen1]

Normally this should work. Which engine did you have loaded?

thanks for the response. but where can i see the machine name? is it at the bottom of the engine button menu? i can see fairymax 4.8 there. is it the name of the engine? thanks