spawns at 22:00 (nighttime) in game. Despawns at 07:00. He stands inbetween a group of guys under the stone archway east of the altinova arena.

Here he is, not on the main road but walk to the South Gate, take a left just before Abdul Jaum - up the stairs > walk between the 2 big guys towards the corner. Next to the stairs, before the red cloth hangings, are two villagers, he spawns between them - but only at NIGHT. Be fast with the amity game - you will need 400.. before he despawns at 7.00. The post of Suricata gives the best favor.

The knowledge for the Altinova Arena can now be acquired from Abdul Jaum, requires amity.

Link to the update notes below for reference
https://www.console.playblackdesert.com/News/Notice/Detail?boardNo=9272&countryType=en-US&boardType=0&searchType=titleContent&searchText=Telshir&currentPage=1

If Telshir has not spawned, Get the knowledge from Abdul the skill instructor. Worked for me. Thanks Mr Tacos

Not working anymore; need 300 amity for Altinova Arena.

The Complete Guide to Finding Telshir:
Do Altinova Arena knowledge. Get the knowledge from Abdul, the skill instructor, so when Telshir spawns, you don't need to make an amity game with him and save your energy to get other knowledge from him.
There are two ways to find Telshir: from the location of Abdul Jaum or  from Borondo, which is much easier. 
Look at photos: