Fixed effect with R, replication of dataset

Question

for my bachelor thesis I am currrently trying to replicate the regression of this paper "Determinants of Foreign Direct Investments: Dynamic Panel Data Evidence", Erdogan and Unver (2015). They state to use fixed effects: Mathematic model of regression. However I don't know for which variable to use fixed effects and how to do so in R. This is their regression table: Regression table to be replicated. They used data of 88 countries over a roughly 30 year period. I downloaded all the data from the data bases that they cite and use the following code right now for the replication of model 1:

m1_rep <- lm(fdigdp ~ lag(lpcgdp) + lag(gdpg) + lag(fdigdp) + lag (enrol) + lag(finop) + lag(marketsize) + lag(creps), data = df_replicate)

Do you know how I can use fixed effects here and for which variable I have to include them?

I am more than thankful for every support!!!