你说的这个老外有“冒牌”的嫌疑。他的句子有些像Chinglish。你看看词典的标准表达方法。
《麦克米伦词典》
friend: vt.
to add someone to your list of friends on a social networking website
My mother-in-law friended me, and I didn’t know how to say no.
由此可知加微信的标准说法是 friend sb on WeChat.
你能加我的微信吗?Can you friend me on WeChat?
有个帅哥想加我的微信。Some handsome boy wants to friend me on WeChat.
我们加个微信吧。Shall we friend each other on WeChat? Let's friend each other on WeChat.