Whilst adding an oil degrading microbial assemblage can help degradation rates much more important is providing inorganic nutrients, correct water relations and aerobic conditions. For references I suggest you look at the Clu-in website. Just do a google search on Clu-in and you will easily find it.

first of all you, you need to know whether ur  bacteria have bioremediation capability or not? after that, if the results were ok, then you must prepare lots of bacteria in the right media then centrifuge it and collect the bacterial plate and dissolve it in the di-water and propagate it in the farm

Depends if you want to bio augment with exogenous microbes having remediation capability (some commercial product claims to do this). Else you need to isolate the bacteria from contaminated soil, test for remediation capability in right media, and propagate before applying to the soil again. To look also for other remediation factors like like pH, CNP ratio, etc. Agreed with both Alan and Reza. Look up in CLU-IN for more info. For phyto, my experience is only to biostimulate the existing bacteria at plant roots.

prepare stock bacteria in liquid form

First off all you have to decide what bacterial population u want in your soil (for eg. 10000 cfu/g), obviously it should be enough to colonize and establish itself to the contaminated soil. Then you need to grow bacteria or consortium in appropriate culture medium like nutrient agar, lb etc and either you can add the medium itself or centrifuge cell mass ad re-suspend it in Distilled Water  and then add to soil. You can have an estimate of bacterial population by taking OD and then cell suspension in DW may be diluted or concentrated (by adding more cells) to get desired OD and then add it to soil to get desired soil count.

But before mixing anything liquid in soil one should calculate water holding capacity of soil particularly for pot studies. if the volume of liquid used is very high with respect to WHC it will flow out and microbes will also be lost. Similarly, if the volume of liquid is too less proper mixing will not happen and some areas will have high inoculum whereas some will have low. Usually vol of liquid should be 40-60% of WHC,

Islam, my advice would be to follow the recommendations given by Prof Newman. 

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Hi Islam

Firstly, check the hydrocarbon degrading efficiency of the isolated bacteria and then check their interaction  with plants used for remediation of oil contaminated soil.

Then after you can design a setup of to remediate  oil contaminated soil using bacteria and plants.

 In addition to all above mentioned it is better to use bacteria in a carrier based form

Hi Islam, Hope you finsihed your experiment. But just to share my opinion. I liked Prof Newman suggestion. Clu-in is good guide. I can share my experience, which may help you in your lab scale experiment in future.

In high oil contaminated soil, you better follow (i) partial inoculation method/adaptive technology, which is: take certain amount of that soil and sterile it by autoclaving. Then you inoculate desired bacteria directly from your liquid suspension (preferable lite buffer or DW (for immediate use)) into that soil. Incubate them, monitor them whether the count increases. Then you mix these incubated soil to the experimental soil. This will prevent the direct toxicity often caused by direct inoculation by liquid spray, and (ii) carrier based inoculation using corncob powder, clay powder etc. Thanks