How can I make non stationary data into stationary?

[sbkb]

i have this regression inflation c nominal effective exchange rate + interest rate + industrial production.

When i tested this series for stationarity i get a result that all are integrated of (I)1, they are stationary in their first differences.

My question is what should i do, how to fix this issue?
Should i include all variables in logs (ex. log(inflation) c log(nominal effective exchange rate) + log(interest rate) + log(industrial production), or should i do this: d(inflation) c d(nominal effective exchange rate) + d(interest rate) + d(industrial production) including them like first differences?

Is (LOG) going to fix the non stationarity of data?

[sbkb]

Can somebody please answer me?