Essentials of each process can be found in guideline dedicated for foreign participants (here)
In accordance with the point 5.2.2.4 (3) of Capacity Market Rules, the offered volume of capacity obligation shall be not less than 2MW.
In order to submit offers in the pre-auction, you will have to create an account in the Register - PURM and submit an application to be assigned with a bidder role in relation to your entity. The bidder role has to be established minimum 1 day before pre-auction. For that purpose you will need to acquire a Power of Attorney. PoA shall be issued on the template Appendix 4.3 (here) and has to be signed by the representants of the capacity provider. User manual, which describes the abovementioned processes, can be found here. Moreover, in order to establish an account in PURM and submit applications/offers etc. you will need the qualified electronic signature.