(Im sure this part below can be shortened)
You want to lay the horse, So click on the red square inline with the horses name this will bring up the current odds you will see a box with Backers odds if this is above 3.0 we need to change the odds to 3.0. now if the odds are less then 3.0 then we would lay the horse at this time, enter the amount you want to use as a stake in the Backers stake box that you wish to place and then click place bets tab job done.

 

But should the price be above 3.0 then after placing the bet we need to tick the box that says KEEP.

This will allow us to go in play, now we hope the horse runs very well but does not win then we should get matched at 3.0

 

Now the bad part should the horse win then we will lose 2x our stake so if you lay the horse for £10 and should it win you would lose £20.

 

If the horse runs very bad and does not go as low as 3.0 in play then your money will be returned to you.

I hope this helps you get started