If they are all nailed then its a bit harder.
How to remove bottom row of roof tiles.
Removing a tile from the roof.
Individual hanging slate removal sometimes a good tactic is to place a large 300mm 12 hacksaw blade in a hacksaw blade holder and cut through the two nails that hold the slate rather than use the slate rip and risk further damage.
Position the first roll of underlayment at one side of the roof perpendicular to the lower edge the eave of the roof.
Generally it is not necessary nor desirable to nail every single tile on roofs nailing as described here will provide a fully functional roof while allowing individual tiles to be remove later if necessary.
Once you have safely gotten to the broken tile you ll need to slightly lift the tiles that overlap the one to be removed.
Some of the tiles may have clips or nails holding them but not all.
Begin by lifting up the next door overlapping tile.
You may be able to prise the nail free by lifting the bottom edge then again it might snap the tile so have a spare handy.
You simply slightly lift the tile at the rear of the one you want to move and then lift the front and slide back the lower tile.
This will expose the nail on the tile on the bottom row.
This will lift the overlapping tiles on the row above so the tile you want to remove should come out easily.
They are not hard to remove either the hardest part being lifting the first tile.
Every tile of the 2 rows at the eaves both the half and full tiles those up verges and along the 2 rows at the ridge both the half.
How to replace a roof slate.
As you roll out the underlay keep the bottom edge of the material aligned with the edge of the eave but above any metal or synthetic edging that may cover the borders of the eave.
Then use a brick trowel to lift up the broken over the baton underneath and slide it down and out.
This video from bunnings shows you how to take a tile off and replace it prop.
You may find that you need to go up a couple of rows to find an un nailed one then then work back down.