Sewing surcingle's and leg straps into horse sheets?

I just bought a fleece show sheet and fly sheet for my horse and need to sew in surcingle's and leg straps (I paid almost nothing for them!). However, I'm really unsure how to do this? I was wondering if anyone had any good tips or know of any websites that sell complete kits to do this? I plan on using them for shipping or when the horses are in their stalls or at shows but would like to make them as heavy duty as possible. Any tips would be great!