What I have to do for Visa

I dont think entry visa is enough if you want to come and stay... Depends on the purpose of stay. People outside the Europe need to have a legal reason to apply for temporary residence permit. You can apply for residence in Tehran, tehran.mfa.sk/en/home, but they will only accept the application if you bring: valid passport, confirmation of the reason (document proving a study, work, business etc), criminal record of Pakistan translated into Slovak by Slovak court appointed translator - duly veryfied, and rental agreement confirming your place of accomodation (with notarized signatures and a deed of property "LV"). you also need around 200 eur per month for at least one year of your stay (bank extract). The administrative burden is quite heavy, so it is necessary to be well prepared in advance. Otherwise you can lose money and be rejected.  Good luck.