New to Chihuahua training... Any help is appreciated.

[khoard]

I have had my Chi for 3 weeks now. Hes just over 4 months old. The lady I got him from never had him outside. He just went to explore the first time outside Monday. He is timid when people try to pet him or walk by him so I just opened the door to get him to go try it out. He will jump in the bed and cuddle with the kids and I, but thats the only time we can get close to him. The questions I have.... How can I get him where he's not so timid? How can I potty train him better? He is kinda pad trained. He uses it once in awhile. Never poops on it. Any other tips are greatly appreciated.