You will require an interface kit from your TPSi to the robot.
I would recommend the Fronius RI/IO Pro interface and you will need the associated cable set.
Depending on how many welding jobs you want to be able to access and what other inbuilt functions and external tools (clamps etc) you want/need, you may also require an IO expansion module for the UR.
I would also recommend you choose the following.
Choose the UR10 over the UR5
Install the Fronius PMC weld process option
Use an MHP550i water cooled machine torch rather than a manual torch
Use a spring counterbalance rather than mount the torch on the arm.