Lean to use route plotting software on your home computer, which is easy. Many have learned; so can you.
is of course advice you should heed but you may not always have the luxury of sitting in the front of your home computer. Or maybe you just can't be arsed to do it that way? If so, here's how to do it on your device...
Touch the road you want to go to on the device's screen. You'll probably need to zoom in and to have loaded the detailed maps, of course. This video, though for a different device, shows you how. Your device might be different but you'll work it out, I'm sure.
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Use the device's ability to find a specific address / 'Where to' function, where you can enter an excact address / post code. Of course you'll need to know the road's name / post code or you'll just have to enter Ryhll or Northampton or Chalfont St Giles or wherever it is you want to sort of go to, whereupon the dumb (but really very clever) device will just take you to the town centre, it requiring some clear input from you (the much cleverer) owner if you want to go to somewhere more specific than the town centre.
Use a bit of common sense. As you approach the town, instead of following the magenta line to the town centre - created by the device (only as you had given nothing better to work with) - strike off of your own volition in the direction YOU want to take. If you find the device bloody annoyingly keeps routing you back to the centre (but, hey, let's not forget it was where YOU told the device YOU wanted to go) learn to use the skip waypoint / do not auto-recalculate functions.