A client hired me for a job. Then they have been so over busy that I couldn't started the job. The client declined the proposal, however they are willing to finish the job. How should proceed ?
If the client declined the proposal, then there is no contract.
If you have communicated further with the client and she wants to hire you, then she may create a public job posting and send you a link to it, and you can apply to it.
Or - even better - she can create a private job posting and send you an invitation to it.
Or she can send you a direct hire offer.
On the client-side interface she will see "Hire" and "Invite" buttons.
The best way would be for her to create a private job posting and send you a "Hire" offer.
Or use the existing job posting if it is appropriate and open, and click the "HIre" button next to your name.