Help please!!!! Nutes...

Hello, I know that it might be a stupid question but i'm a newbie and I need some help with fertilizing. My plants are 4 weeks old, are they to young or i can start? they are outdoor in pots with soil. Today I bought a liquid fertilizer Advanced Hydroponics of Holland Dutch formula, I wanted to know how often I have to use it, if once a month or every time I water. Oh and the label says to give different amounts of fertilizer during flowering stage and end of flowering stage, what does it mean for end of flowering stage?? Has anyone ever used this fertilizer?? is it one of the best?? sorry for the stupid questions and for the grammar but i'm italian.

thanks

If you have a flowering formula you shouldn't be feeding it at all and get a grow nutrient with a high nitrogen number. Start with the minimal dosage or even cut that in half and move up till your feeding full strength so as to not burn your plants