Need some advice

I have purchased a set of Zent cams ‘Fast Road’ for the Zetec silvertop <05/98 which has the Hydraulic tappets. The Haynes Manual states on refitting “Note: if new hydraulic tappets are being fitted, they must be charged with clean engine oil before installation” I might be stupid but I do not understand how this is achieved?

This is my first attempt at changing the cams and I have spent the last week removing the rocker cover, spark plugs, timing belt covers etc. I fitted the dial gauge and after some head scratching I’m confident that I have figured out the timing and what’s involved in the procedure. The car has now been sitting in the garage for about three weeks since the last engine start and it has occurred to me that the oil may have drained out of the oil galleries and the tappets. The manual states that the engine should be primed before starting but I can’t find any sensible reference on how this is done on a Zetec?

David 2001 4/4 4 seater.