How can I replace both antennas and fix data signal?

I have a galaxy s4 i545. The data signal drops all the time. I thought it could be a kit kat software issue at first, but its not. The phone is now updated to lollipop and the same thing happens. I can only reset the phone to get a data signal back. Also the 4g connection is slower than the 3g connection most of the time. It can never stay on 4g, when it does the phone gets hot. It always switches back to 3g and then the data works again. I took the phone apart and saw that the left red antenna is missing the connector on the end of the flex cable. Its just an open end wire kind of touching where it should be connected. I ordered a new left and right antenna flex cable. Is it just connecting each end? Are there any other steps or factors to consider to fix this problem? I don't see answers for this kind of repair anywhere on the internet. Please help.