Learn how to use the IF function to create an IF THEN ELSE statement.
The IF function has the following syntax:
IF( <this is #true>; <then #do()>; <else #do()>)
IF( (#Example!Input <= 5); (#Example!Input + 1) ; (#Example!Input - 1) )
IF(CONTAINS(#Input; "words"); "yes"; "no")
IF( CONTAINS(#Input; "words"); REPLACEALL(#Input; "words"; "text"); (#Input))
Please have also a look into our Community thread How can I 'pipe' or 'join' multiple formulas so I can do several IF statements?.