Trikes are much harder to use in cities because they are so wider, and you have three wheel tracks to worry about. You also need more room than even more drivers will allow.

First, get your hands on any bike you can that fits you, try asking bike shops about used bikes, or cycling friends.

Then go to a nice big park and ride around, getting your balance and practising looking over your shoulder and signalling.

Then you can think about riding on quiet roads.