The syringe and bit of tube you bought are to assist in filling the system-and not a 'bleeding kit', this is where some confusion comes in
1 attach syringe to tube, dip end of tube in bottle of brake fluid and draw it up until full, hold tube pointing up and 'gently' purge it of air (there will always be a tiny air bubble at the end of the tube)
2 attach the tube to the bleed nipple (the bleed nipple should be open by 1/4 to 1/2 a turn only), open the banjo bolt a couple of turns, now squeeze the syringe (about 2mm, count to 10, and repeat, the key is to do this whole operation slowly)
3 repeat the gentle squeeze until fluid shows at the banjo end, now tighten the banjo, go back to the gentle squeeze again-fluid should fill the master cylinder and start to fill the reservoir.
The back bleed method should really be called the 'back-filling' method, this method of filling the hydraulic circuit Helps to eliminate air bubbles from the other method of 'top filling'
If you try to fill any slim vessel with a liquid/fluid from the top then air is introduced by the fluid 'glugging' down into it. Air is buoyant in a liquid and will try to 'climb' to the top. By filling from the bottom (slowly) the air will be pushed in the direction you want it to go-up
After the system is 'filled' it still needs to be bled
Which is Part 2 (tune in next Wednesday for the second episode)
Hope this has helped-I need a lie down now