Hello. I rolled over a 401k from an old employer into a traditional IRA I have. Is that considered a taxable contribution to the IRA?

No, a rollover from a 401k to a Traditional IRA is not considered a contribution to the IRA.  It is simply a rollover.  

If you have received and entered the information from Form 1099-R reporting the distribution from the 401k, then that is all you need to do within your tax return.  Be sure you answer any follow-up questions that may come up with regard to the distribution. 

You do not go to the IRA section and enter the amount as a contribution.  That section is only used when you personally make a contribution to an IRA.  

A rollover is not a regular contribution to an IRA.  Do not enter a rollover under Deduction & Credits, enter it only by entering the From 1099-R and indicating what you did with the money.  The amount distributed form the 401(k) will be included in box 4c of Form 1040 but the amount rolled over will be excluded from the amount on line 4d.  The word ROLLOVER will appear next to the line.